BMR calculators are all over the internet, and I’m sure that’s due in large part to it being such an easy formula to calculate (look it up). We input our sex, birthdate, height, and weight into the app, so figuring out user’s BMR is as easy as running a single mathematical calculation, then dividing it by 24 to get the number of calories burned each hour (or divide by 1440 to get a rough minute-by-minute calorie count) w/o any activity at all.
I don’t know if the band or app are trying to take anything like that into account at all, but it doesn’t seem like it. I did not burn 160 calories today; I burn half of that each hour just by breathing.