burning calories with RPM session

I think i am addicted to the gym nowdays..and you guys might think that i am crazy...hahaha...yesterday was damm tired. I went to gym at 6am morning to meet up with a personal trainer for my training session. He guided me on how to build a v-shaped body, abs and broden the shoulder. It was a good training and i ended at around 8am and proceed to work after that.
Later after work, my buddy asked me to go again accopanying him for workout. Well, going gym twice in a day...going crazy already...but i plan to do cardio only...no heavy weight training. When we reached the gym, the RPM session that being conducted seem so accelerating with hot musics and basses. We decided to join the next RPM session which will start in half hour. The instructor name is Marcus and he is damm fit. Cycling for 45 minutes would burned up to 900 calories if we follow exactly his steps. But i guess i couldn't go up to that level, err...maybe 500 calories burned only. It was tiring and i really exhausted.