How many calories does belly dancing burn?

Anyone ever ask themselves that or rather replace belly dancing with spinning, ball room, zumba, etc. When I'm on an excercise machine , such as the 'elliptical', it automatically calculates my calories burned for me so that when I put it into the system-when I log my exercise, I know that it's more or less accurate. When I put in "belly dancing" , let's say 60 minutes, it gives me 376 cal. or something, but how do I know that's actually the amount. I've put in 40 minutes on the elliptical before and had MFP calculate and it gave me some ridiculous number like in the 600's. While I'm willing to admit that burning that many calories , in 40 minutes, on the elliptical is in the realm of possibility. I certainly didn't. Not even close.

So my question is , for general things that can't be calculated on the machine, how do I know that MFP is giving me a more or less accurate amount when I plug the numbers in?