Dance Dance Revolution

I'm sure this has been asked to death, but I wanna go into my own details about my DDR workout, so I thought I'd start my first day here asking about it!

I do it on the hardest level, with the arrows moving at 2x speed, for about 45 - 55 minutes straight. I never change the song so there's only about 30 second between each song, and during that break, I keep moving (usually doing jumping jacks or jump rope, unless I have to get a drink, and even then I walk around my bedroom while drinking) Even when there aren't arrows on the screen I dance around on the mat. I jump and move a lot. My heart rate is high the whole time and I sweat so much. My legs are burning during the entire thing, too. It surely makes me sweat more than running in place or rope jumping for 45 minutes ever has. The calorie counter says I burn 1000 calories, but I know it isn't that much. I always guess it's between 300 - 500 calories, half or less than half of what it estimates.

Does this estimation sound good? And, I do this on top of 20 minutes of strength training and I eat about 1400 calories a day. Does this sound good to lose weight?

I'm 138 pounds now and only 5'3". I'm aiming for 115 )

EDIT: Yeah, I do it on challenge. I move and jump a lot. And, I also mix up my cardio. Some days I'll use my stationary bike, others I'll do DDR and rope jumping, or just rope jumping or running in place...etc etc.

EDIT: I have Dance Dance Revolution: Extreme 2 for the PS2 )

Edit: I have looked it up on Google. The fitness site Livestrong says that in one minute on the hardest level you can burn 8 calories. My songs are about....1.5 - 2 minutes so I guess it's about 10 - 12 calories per song.