Trusting MFP when eating back?

avskk

I log my exercise through the FitBit dashboard (and the 'Bit records my movement, of course) and eat back some of my FitBit adjustment sometimes, but not all of it all of the time. It's basically a buffer if I'm legit hungry after an active day or strenuous workout, but otherwise I leave it alone. I don't log exercise through MFP; I did so a couple of times and the calories it gave me to eat back were insane (like 500 calories for ~30 minutes of lazy-assed swimming).