Calories Burned During Kenpo X/P90 X?

I have frequently been working out lately, every couple of days (Probably anywhere from 2-4 times a week) I will do Kenpo X from P90x. I have read online that people generally burn 600-700 calories with this exercise. I did the calorie count online at the p90x "calories burned" website and it told me I burned about 900 calories which seems way to high.. I am 6'0 and 190 pounds. Part of the reason I feel that this exercise is not as big on calorie burning as the websites say is that I don't find it to be very difficult. Originally when I started, I was very winded, but now I flow very easily with it and am able to do the same amount of reps as everyone in the video. My Heart Rate fluctuates between 160 and 180. So obviously I am winded, but it does not exhaust me. I was wondering if anyone could give me a ball park on how many calories I might be burning in one of the Kenpo X Videos? Thanks so much.