There is no useful reason to subtract exercise calories burned from food. That is backwards. It really does that?
You should subtract food from exercise calories burned (plus your daily BMR as well). Adding up all your burn sources and deducting food, you want a 500 calorie per day deficit to lose an average of a pound a week.
Subtracting exercise burn only from food eaten actually tells you nothing whatsoever. I could outline three people with the same result from that calculation - one would gain weight, one would lose and one would maintain.
You need to consider BMR, not just exercise.