Burn meter question???

Ok, why does my burn meter tell me different figures from one week to the next? For instance, last week on Monday, after putting in my activities, the burn meter said I will burn 2,640 cal that day. This week (Monday) I logged the same activites and my burn meter said I'd burn 2,630 cal that day. Same info. in my account settings and everything...

Tuesday (last week) after adding my activities, it said 2,490. Yesterday (Tuesday), same activities and it said I'd burn 2,470.

Wednesday (last week) after adding my activities, it said 2,340. Today (Wednesday), same activities and it said 2,330 is what I'll burn today.

 Why does my burn meter change my calorie burn when the inputted info. is the same???? Why does it keep decreasing? Anyone???

I'm not sure but it could be because it assumes you are steadily losing weight and less weight = less calories your body needs to burn for it's necessary bodily functions. But it's just a thought. 

Thanks! That makes sense.

What kind of things do you put in your burn meter? Do I put things like laundry and walking around at school (I'm a teacher)?