Help me understand the weekly goals calories burned

Hi all,

I'm a MFP newbie and I'm puzzled about something. My exercise goals as calculated by MFP for a weight loss of 1 lb/ week is exercising 3 times per week for 30 minutes each time burning 500 calories per week. I exercise approximately 5 times per week, typically M-F for about 22-33 minutes each time. So say my last workout for the week is Friday and the accrued calories burned is 1200, by Sunday that 1200 turns into 1400 even though I haven't worked out/logged any exercise. I don't understand that. Shouldn't it stay at 1200.

Can someone please explain this?

Thanks