Kickboxing and Body Media Fit

Hi everyone. I just got a BMF and I used it today for my first workout. Now, the question is, how accurate are the calories burned? I;ve heard that BMF is less accurate on certain exercises. I'm pretty out of shape so while I do take an hour long kickboxing class, I take quite a few breaks anywhere from 30 seconds to about 2 minutes. According to BMF I burned 402 calories which is what MFP says I would burn in about 34 minutes of continuous exercise. Does this seem about right? Any help would be greatly appreciated. Thank you!