Confused?!!

Tylerbrook01

So this morning I ate breakfast which was around 300 cals and that's all I have logged so went for a walk down to the shops synced my Fitbit to check how many steps, and when I went back to my fitness pal it's saying I've eaten an extra 100 cals in my net calories? Now how's that? I've only eaten my breakfast so how can going for a walk minus me 100 calories? I thought it was supposed to work the other way around? Any advise would be great thank you xx