Understanding the move circle

I am trying to understand the move circle better. When I look at my calories per day.. the current average is 740. I do not excersize at all. I do not climb stairs. I do nothing more than work. I am a teacher.

But when I compare it to my sister- she regularly works out and has intense physical activity- she may only average 450-500 calories despite 60-120 minutes of working out. She recently competed in a fitness competition and placed third in our region. She is definitely in better shape than I am. I don’t understand the huge difference in our calorie burn.