witch "daily activity" to use when counting steps?

You should choose the daily activity that fits your daily situation best. If you work at a desk all day, then you would be Sedentary. If you are on your feet a bit during the day (they say like a teacher), then Lightly Active would be more appropriate. Ignore the fact that you may be going on a walk or working out once a day. The daily activity means how do you spend most of your day. Then MyFitnessPal will give you a calorie intake goal that better reflects how much you burn during the day and takes the assumption that you do not work out/walk. If you do, then that is when you get a negative exercise amount and get to eat more calories (YAY!). I work at a desk all day, but spend at least 30 minutes working out each day too, but I still list myself as Sedentary. Does that make sense?

Probably can't make math adjustments until a new sync comes in, or overnight.

The MFP activity level expects some amount of walking in your day already, as well as other movement, just NOT exercise.

It's been found by those using activity trackers where the levels seem to top out at - I've usually seen Sedentary from people at 4000 steps.

Then again, steps isn't calories.
Steps is distance.
Distance and time is pace, with weight is calories.
So it can vary depending on what the steps are creating for distance.
And it includes the time after work - which is where people with kids discover that a desk job does NOT mean a Sedentary activity level.

There is more than just step calories added to the BMR to get what is called TDEE - also calories burned processing food (TEF), and standing or merely awake sitting time burns more than BMR (deep sleep burn rate).

So no, that would not be a good formula.

What the activity trackers generally do is use steps/distance to add calories to your BMR, just as you suggest, workouts use either steps or HR based calorie burn depending on device, manually entering for correctness perhaps.
But that does underestimate the day with no TEF, non-step time is given BMR level, ect.

Then that daily total goes to MFP to correct itself.

So you are likely underestimated since non-step based work.

not to poach the thread but my question is similar--I have a desk job, so unless I work out I am getting between 4-5k steps a day. I count that as sedentary, but then track my fitbit to MFP to account for exercise--sometimes is daily, othertimes its not, so I would rather have a daily account of exercise than change my overall activity level.

as for flemmings, you might want to experiment with settings between sedentary and lightly active and see which setting results in the best calorie level/weight loss rate for you. Its a little unclear from me in your post when you are active at work whether it is just lifting or also involves.

192 steps from when it first saw movement until "now" is how long - when is now?

The timestamp on your posting doesn't help for your local time.

Because true, Lightly-active should have more assumed steps that will be done anyway, but depending on how it does the math, and true on comment above it'll adjust anyway, that won't be the same as the day draws to a close.

So last time you didn't give screen shot of what was showing up in the Exercise Diary.

Was Circuit training already there?

Because with only 12 exercise calories added in to simple display, that could have been the exercise 150 + negative adjustment 138 = 12.

But now on Sedentary, it sees that more of your steps count towards extra calories, so bigger adjustment (besides there being 7564 extra steps). So 150 + 320 = 470.

Also, your initial eating goal did indeed change because you changed Activity level.
Steps done won't influence that directly.

You also have to remember to click on that "!" for more info as to time of last sync, and amount.

And those 313 calories Pacer is saying for steps/distance must be for just that - not the daily calories that your other post screen shot showed as daily adjustment on MFP.

Sedentary is actually a better option WHEN you are syncing in an activity tracker - which this is basically acting as.

It has more to do with what happens at end of day goals and adjustments and corrections.
If you enjoy math and want to see what's going on, this FAQ applies to your device too as far as math is concerned, so read the 2nd section.

http://community.myfitnesspal.com/en/discussion/10098937/faq-syncing-logging-food-exercise-calorie-adjustments-activity-levels-accuracy/p1

Just estimating here, at say 19:00 hrs (so 10 more min), or 79.2% of day done, leaving 20.8% left.

I notice the new Sedentary goal is 2090, last time it was 2100.
But Lightly-Active matches at 2340.
I'm guessing it was already at Lightly-Active - and your weight has gone down.
Changing to Sedentary allowed MFP to recalc your eating goal.

Can't do any example math without knowing your deficit selected (maintenance?), or at least MFP BMR being used.

That's actually a very useful way to use it - when I get into big cardio mode I do too.
I use a spreadsheet to give me the deficit amount depending on how much cardio burn I've done.
That way bigger burn days can have bigger deficits, rest days can have none.
So that much is left in green. To anyone viewing it, they might think I'm leaving my deficit bigger, but there is none built in.

What I was attempting to do prior.
Sedentary Maintenance 2090 / 1.25 = 1672 BMR ( x 1.4 Lightly-Active = 2340 maintenance, so that's correct)

2090 / 24 hrs = 87.08 cal/hr burn rate at sedentary
The 19 hrs up to sync would have been 19 x 87.08 = 1655.
320 cal adjustment with 5 hrs left. 5 x 87.08 = 435
1655 + 320 = 1975
1975 + 435 = 2410 estimated daily burn.

So your device at the time above must have reported to MFP that you had burned 1975 calories at that point, based on purely I'm guessing steps and more importantly distance.
Device reported 1975 - 1655 MFP expected at Sedentary rate = 320 adjustment up.

Eating goal 2090 + 320 adj + 150 exercise = 2560 new eating goal

2560 new goal - 1411 eaten already = 1149 left to eat.

So the only thing I'd be concern with is the accuracy of the distance on the device based on steps.
If you can adjust stride length, make sure you get that from doing avg daily pace, not extremes of exercise level or grocery store shuffle pace.