Redmi Watch 4 calorie count?

Hello! I got the Redmi Watch 4 and I am wondering how calories work. It shows I've burned 800 calories, when I haven't worked out and only walked 12k steps. It says it counts resting calories too but surely my resting calories (bmr) + active calories cannot only be 800. So what's the case? Is that number on top of my BMR ?

BTW I know calorie counts on smart watches are not really accurate, I just want a general idea and I need to know how it works.