Help with weight losing!?!?!?

I have this doubt related to BMR and my activity levels. OK BMR clocks in at aprox 2156 calories. Why would i need to consume those calories if my body already has them stored? Ok let's say i would consume those calories, then started doing exercise and burned off 300, would i be at 1856 calories thus not being on par with my bmr?

2017-04-11T00:37:33.809Z