Zumba & HRM calories burned???

ebonyroche

I just started the Zumba Activate and it's 45 mins and my hrm is saying I burned 300 calories. I am 300 lbs and 5'6, it seems like I should be burning alot more, right?? I can't jump around to much because I live on the 2nd floor and I workout early morning plus my knees aren't that good but I try to put as much effort as possible. Is this happening to anyone else? I'm expecting to much to soon?