HELP PLEASE!!!

So- I just bought the New Balance N4 Heart Rate Monitor, and I have it all programmed (my height, weight, target heart rate zones, the time...) but I have NO clue how to use the damn thing! Can anyone help me? I wore it tonight for the first time to a class at my Gym, and when I checked it at the end, it said that I burned 49 calories. I am here to tell you that I EASILY burned at LEAST 5 times that amount, which only leads me to believe that I am doing something terribly wrong! What I did was, right before the class actually started, I hit the "start/stop" button (upper right hand side). Is this wrong? Does anyone have any insight on what I may be doing wrong and how I can figure this dumb thing out?? I'd like to think that I have the technology thing down, but as of this evening the score stands at a strong: Heart Rate Monitor-1, Jamie-0.

Thank you so much for any advice/tips you can offer me! :grumble: