[Tagging] building:levels and flat roofs

[contrapunctus]

I previously discussed this subject on IRC, but would like to revisit it here. Please consult this image [1] and suggest how its levels should be tagged -

1. What value should be given to building:levels=*?

2. Should roof:levels=* be used? If so, how?

If I remember and understand correctly, the consensus on IRC seemed to be building:levels=6 (B + C + D + E + F + G), with A being tagged as a building:part=yes + building:levels=7.

I noted back then that this contradicts the building:levels wiki [2], which states that building:levels=* should not include the roof level.

I followed the advice given on IRC, but recently noticed that OSM Buildings [3] renders an extra roof level beyond the value of building:levels [4], rather than including it in the building:levels count.

Thank you.

PS - is there a term for the "A" section of the photographed building? i.e. a structure that covers the stairs, with a door or doorway, in some cases housing water tanks on the roof, which may be accessed via stairs or (more commonly) a ladder.

[1] https://wiki.openstreetmap.org/wiki/File:Multi-level_building_with_flat_roof_in_Adarsh_Nagar,_Delhi,_India.jpeg

[2] https://wiki.openstreetmap.org/wiki/Key:building:levels

[3] https://osmbuildings.org/?lat=28.62160&lon=77.29047&zoom=20.0&tilt=35&rotation=10

[4] https://www.openstreetmap.org/relation/16404734