Calories burned using 30 day shred level 2

I don't know about formulas. I use BodyMediaFit which tracks everything I do. I also use a HRM sometimes, but my HRM doesn't tell me calories unless it knows what activity I'm doing and it is using GPS to track my movement. I use the HRM to see my cardiovascular improvement over time.

So, for me, my BMF gave me this data for Workout 1 - 186 calories burned (this was my third time doing the workout), for Workout 2 - 157 calories burned (this was the fourth time doing the workout). In both cases I was using 5lbs weights.
I did notice that my calorie burns for the workouts increased some (between 10 -20 calories) as I became more capable. I should also mention, I do the workouts three days a week and not every day.