Custom Calorie Setting

I haven't been able to figure out a good way to incorporate the exercise that I do into the app and after a few days of eat at or below my "Calorie Goal" (which I increased from the original.) I noticed I would get very hungry and irritable between meals. It got to the point of not being able to handle much except getting food.

I lift and do light intensity cardio 3 times a week and I do High intensity intervals training and abs 3 times a week. I can enter the cardio and what the machines tell me I burn but I can't compensate for my lean muscle mass and the resistance training I do.

I recently found this on a thread:
http://www.freedieting.com/tools/calorie_calculator.htm

I noticed the Katch-McCardle formula under advanced options and knowing my body fat approximately I gave it a shot. I am 5' 10" 212lbs and about 18.5% body fat. This formula gave me around 2500 calories a day to lose weight.

Should I set this as my goal calories and just not bother imputing my cardio? Is there any other option that anyone can think of?

I was really confused when i first set up my account because I work at a desk job. I made it under the 1900 calories but I couldn't do it on a daily basis.