Step counting vs activity level

SoulOfRusalka

So now that MFP can sync up with my iphone to count my steps, I'm confused about how many calories I'm actually burning.
What I used to do was set my activity level to sedentary, and count any "extra" movement as calories burned. So I would walk 4-10 miles a day, and MFP would give me 100-150 extra calories. (TDEE 1700-1800 ish?)
But I found a thing online that said that walking that many miles is lightly active (I think), so MFP says my TDEE is always 1800 if I set that as my activity level. 200 extra calories! Wow!
So, I should stop with the step tracking now, right? It's giving me like 90 calories burned for walking 4 miles, but I shouldn't count those miles since they're already factored into my activity level, correct?

(This is only a difference of a few hundred calories and it doesn't really matter since I'm still eating *less*, but I always thought the step estimates seemed low when my activity level was set at sedentary. Logging walking as an exercise, I would have burned about 60 calories per mile, and according to the step tracking it's more like 20 so I'm not sure which to believe.)

Sorry if this is confusingly worded. Just curious.

PAV8888

Enable negative adjustments when you synchronize with an external tracker.

that takes care of not double-counting whatever is built into mfp activity levels.

But it simultaneously off loads the evaluation of how many calories you've really burned to that external tracker since it essentially overrides whatever mfp is calculating based on the information you provide in Mfp