Stair Running question about accuracy

CatBird128

I'm trying figure out the best way to enter stair-climbing on the myfitnesspal app. I do 60 minutes of going up and down as fast as I can - I don't turn around, I'm backing down the stairs with my hands a few steps up from my feet as I go. So this way I can do a lot of stairs reps in an hour and can safely push myself to go faster without fear of falling.

But obviously I start out running and by the 45 minute mark my pace has slowed considerably. If I enter it as Running up Stairs it would be just over 913 calories for 60 minutes, but if I entered it as Walking up Stairs it would eb 488 calories. Should I enter it as 30 mins of each to be more accurate?

Also when I enter stair running for 60 minutes into any other online calorie program the amount is way less than the 913 calories that FitnessPal has in the database. Where does this number come from? Did someone enter it based on an estimate or are exercise calorie rates actually confirmed before we're all able to use them?