Workouts

I just finished my second day of working out. I went 26 minutes yesterday on a bike and went 30 minutes today. I went at a faster pace than yesterday so my calories burned went up. The question I have is how much did I burn? The bike said this morning that I burned about 70 to 80 calories while Sparkpeople.com site tells me that I burned a little over 300. That is a huge difference. I wonder if I am just not going at a fast enough pace to really burn 300 calories? Any insight on this?

dj