This is only if you use the Just Sweat mode in the Just Dance games. It's just a little something that'll make it easier to track your calorie amount on MFP.
HOW TO TURN SWEAT POINTS INTO CALORIES:
"The equivalent for a typical overweight person to take sweat points and turn them into calories seems to be, after some runs with my various tracking equipment, about 4.2:1. That is, you take the sweat points, divide by 4.2, and get your resulting calories. So if you did a song and burned 420 sweat points, that would be 100 calories."
http://www.bellaonline.com/articles/art175545.asp
Basically, every 4.2 (just say 4 instead) sweat points equals 1 calorie. Get the number of sweat points and divide it by 4.2 and you get your calories.