1200 Calorie Target and BMR

Hello!
When I first signed up to MFP, the app calculated My calorie intake to be 1200. Personally I'm finding it so hard to just eat 1200.

I calculated my BMR and it was 1579.55.

BMR x sedentary (1.2) was 1895.46

BMR x moderatetely active (1.55) was 2448.30

I'm trying to exercise as much as I can, like for example this week I worked out Monday-Thursday. So I was able to eat more than 1200.

However, today has been the first day I'm planning to do no exercise at all. And I've just had lunch, and once I have dinner I'll be over the target.

SO...... Should I adjust my calorie target to my BMR? or keep it at 1200.

I'm so confused!" O_o