Calories Burned (site vs. workout reading)

lgreen37

Not sure of how many calories I'm burning -when I put that I've been on the stationary bike for 30 minutes at a fast past - it states on the site that I burned over 800 calories - when I actually am on the the bike the calories stated burned are no where near what the site states. I have been guestimating until I can get the "BodyBugg". I think that will really help.
Any suggestions as I wait?