Calorie credits from my Fitbit

Have you synced it up between Fitbit and myfitnesspal ?

First, you should have negative calorie adjustments enabled so that if you're less active than your activity setting expects, it will actually take away calories, rather than read 0. (Yeah, it isn't encouraging to get negative calories, but you should still have it set to give them to you.)

Second, it sounds like you've got your MFP activity setting set too high. 8000 steps per day isn't that many, so you should almost certainly have your activity level set to Sedentary. This won't affect how many calories you are allotted (assuming you enable negative calorie adjustments) by the end of each day, but it will make the estimate of calories remaining better.

Third, just to make sure things are syncing (MFP has had some trouble in this area the last few days), go to the exercise page (or line in the phone app) and click on the 'i' (or the line, if using your phone) and look to see what time it last synced, how many steps it had at that time, and the math MFP is using to compute your calorie adjustment.

I'd recommend that you join the Fitbit Users Group and read the FAQ that you'll find in the stickies there. Here's a link to it:

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