Estimating calorie burn

Hello everyone.

I’m after a bit of help with using FB’s calorie burn estimates. I’m completely happy with the principles of various different factors (weight, age, muscle mass, effort etc) influencing where you are on their scale, but what I’m not clear on - and can’t find any detail about - is what the upper and lower points of the scale represent.

Does, for example, the lower figure represent a 120lb, 25 year old woman with 30% body fat doing only low-impact versions and using only bodyweight? Or using the same amount of weight as Kelli?

My issue is that if I don’t know what that lower point represents, I’m not clear on how far I should adjust for my own variables. I’ve been assuming that because I weigh less than 120lb, I should take the lowest figure as my calorie burn, but on the other hand, I always do high-impact cardio and I normally lift quite a bit more than Kelli (regularly more than double for some lower body exercises - pre-her chronic pain condition). I’m also relatively lean (photo attached in case anyone’s particularly talented at estimating body fat percentages by eye).

Any useful insights? Ideally I think I need to find a doppelgänger in the community who has a really accurate fitness tracker and can tell me where they normally fall on the scale, but that may be a long shot...