Apple fitness app question - total xxx cal at bottom of red “move” section on iPhone app

What are the total calories count at the bottom of the “move” red section mean? Where do they come from and how are they calculated? I am in a fast at the moment and it is showing total 681 calories. To be clear, I am not talking about the percentage of calories against my set goal. I am talking about the total xxx cal at the bottom of the section. Thank you!