Fitbit with MFP

Pang29pang

I bought a fitbit the other day and i have synced it with MFP...should i enable the negative counter...it adds a ton of available calories and everything else to my usual 1200 calories available. I can only assume it is using the calories that i burn and adding it onto my existing calories giving me at times like 1800 calories available still...i am a little confused on how to properly use the fitbit with the MFP..any advice to make these work best?