Find in the calorie burn graph a chunk of night time lowest calorie burn, and figure out the calories / min burned.

Times 1440 - that's what it's using as your BMR.

For all non-moving times possibly. Find some non-moving time at work and see if it is logging that same low calorie burn. Awake and resting should really be higher.
If it's the same as BMR, then the sensors aren't working great for you. Some they do, some they don't. That means days your are more sedentary are more under-estimated. Moving is fine as long as exercise is type it'll be good at measuring, not things like lifting, spin/cycling, rowing.

Now, the other point of that BMR they are using - how does it compare to your Katch BMR value, using bodyfat%?
Many find it will adjust and end up there, some find the sensors again aren't great on them and it doesn't adjust enough.

Are you sure your Katch is correct? Where did you get your bodyfat? I find that the BMF is a pretty good estimate for me, but it doesn't measure everyone as well. I was able to lose just under a pound a week keeping a 500-650 calorie deficit, but I ate pretty clean during that time. I have a hard time losing unless I lower my carbs under about 150 per day.

Looks like you can actually take a pretty big cut if you want, altho I'm not sure why you maintained only eating 1800 the first week. Should have really dropped. Did you also start a new exercise plan? Are you weighing your food or just measuring?

Oh, and I find that mine measures fine at spin and at weight lifting.

Katch is 1401
1.1 cals/min while sleeping x1440=1584
1.1 cals/min also while sitting and reading

Exercise I am doing right now consist of Supreme 90 Day (circuit with weights some days, Tabata day, cardio day etc.), walking the dogs each day, etc.

I am more active than I thought with maybe one day a week under 10,000 steps.

If anything I am worried that it is over-estimating my calorie burns.

So the heat flux sensor doesn't appear to be working for you, they have inflated BMR as basis of non-moving time. Of course the fact they use a lower value than it really is when you are awake may cause a wash, inflated BMR used more than it should be underestimating awake non-moving time.
Now it may take longer for you than normal. Or do you sleep really warm? Hard to measure heat flux if temp outside body is already high.

But that also means like Kate said sometimes it measures some increased values for lifting and spin (mine never did), and for you probably not.

Now, it may be that your exercise time as % of total time, or that calorie burn as % of total calories burned, is minor anyway.

So your hours with circuit and tabata training / 168 hrs in week x 100 = % of time in workout and under-estimated. If under 5%, no big deal, likely bigger variance in your day due to nutritional labels not be dead-on correct.

Are you sure your Katch is correct? Where did you get your bodyfat? I find that the BMF is a pretty good estimate for me, but it doesn't measure everyone as well. I was able to lose just under a pound a week keeping a 500-650 calorie deficit, but I ate pretty clean during that time. I have a hard time losing unless I lower my carbs under about 150 per day.

Looks like you can actually take a pretty big cut if you want, altho I'm not sure why you maintained only eating 1800 the first week. Should have really dropped. Did you also start a new exercise plan? Are you weighing your food or just measuring?

Oh, and I find that mine measures fine at spin and at weight lifting.

I got my BF% from measurements and online calculator. I have just committed to cleaning up my diet. I was measuring everything but only weighing things like meat/nuts/pasta. I will definitely start weighing my more calorie dense things like almond butter.

I have a hard time and tend to get obsessive when I'm really working the weight loss (especially when I'm not seeing results) and was just hoping the BMF would give me real numbers and a clear path of what to do.

Weigh everything you can. I have found that my measuring cups measure nothing like the weights on packaged items. For instance, the rice I cook gives calories based on 1/4 cup or 45 grams. Well, my 1/4 cup measure actually holds 60 grams of rice, and that's not overflowing, just to the top. So I was actually eating 1/3 more rice than I thought. And that's about 50 calories. Adds up.

Edited to add: Not sure about online calculators and body fat, either. Is your Katch way out of line with other BMR calculations or the same? Online calculators measure my body fat almost double what my gym's bodpod measures. Of course, I think mine is actually somewhere in between the two.