fitbit and endomondo

Hi im looking for some help

My Mum bought me a fitbit today :) which made me very happy but its confusing me already.

I dont know how it works to start... does it reset every 24 hours?

And with the synching to MFP and endomondo that I use when running is a little confusing.

I synched endomondo with MFP a while back and now I have synched my fitbit too but am I supposed to sync my fitbit with endomondo or will it all make it double count the calories burned...

So when I went on my exercise diary it subtracts calories from my cardiovascular exercise... why is this??

Anyone shed any light on the best way to sync these with eachother and how to best work with them ??

Thanks