Ok that helps. I'm still trying to understand the elevation bit.

Stairs are based upon changes in elevation, basically it is based upon changes in atmospheric pressure:

https://help.fitbit.com/customer/por...-count-floors-

I walk in my neighborhood a lot which is hilly. And, it definitely counts stairs for those. On the other hand, when I walk on my treadmill with in incline it doesn't count that as stairs since you aren't actually changing your elevation. You can go and name the treadmill as an activity with an incline but it only has a few percentages you can name - I think 5%, 10% and maybe 15%.

Very active minutes are based upon METS. See this explanation:

https://help.fitbit.com/customer/por...ve-minutes%22-

Active minutes are when you are more active than simply slowly moving around the house or office. My Fitbit will count my outdoor walks, housework, and workouts in front of the TV as active minutes. But it doesn't count my slow steps through the office as such, for example.

Stairs - the fitbit counts any elevation change you make while stepping. So hills count. Elevators do not. I am sure of that, because last week I was in a hotel where I had to take the elevator because the stairs were for emergency use only and on most days I got zero stairs that week despite going up and down 4 floors all day long. But at home I usually get a minimum of 25 flights of stairs a day not just because I live in a multi-story house but also because I live on a hill and when I walk my dog I get stair counts from that as well.