Question Regarding Calories Burned Meter

I was just curious if anyone could tell me why my amount of calories burned daily has changed.  I haven't changed my settings and the BMR calculator has said I burn 1890 cals/day and the amount that was on my Calories Burned meter was always 1880.  About a week ago, my daily calories burned number changed to 1860 and just about 2 days ago it changed again to 1850.  Again, I haven't changed any settings although I did lose 3 lbs. which I figure might have affected my calories burned daily...but since I don't KNOW for sure, I thought I'd ask and see if anyone DID know :)

yeah it's weight loss.  It makes me mad, I'm doing so good on a set # of calories, and now my deficit goes down because I weigh less :P  So now that I'm healthier, I have to do MORE exercise to keep my deficit at a comfortable level.

Mine dropped from about 2050 to 1950.  Of course, I've also lost 35 pounds...

Thanks :)  And congrats on the loss!