What are negative calorie adjustments through synced Fitbit?

I also just started using a fitness tracker. I think it adjusts your calories if you tell mfp you are active but the Fitbit shows you are
Sedentary, it adjusts the calories back to the allowance for sedentary

As a new user, I would recommend you enable negative adjustments and use that as a learning tool to inform you how active or not you really are.

I have had a Fitbit synced for two years now. I am set to MFP Sedentary in maintenance. On the few days I mostly work at the computer, I sometimes end up with a negative Fitbit Calorie adjustment for the day. I also end up with negative adjustments when I am sick and mostly in bed all day.

On more active days, I get a couple hundred Calories added, because I am usually moving more than the estimate of MFP Sedentary.

I would recommend reading through the first three posts in this thread on the MFP Fitbit Users group...

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

http://community.myfitnesspal.com/en/group/1290-fitbit-users