Standard Level Numbers

I’m implementing some of the new organization features (many thanks to all who developed those, btw) and am wondering if there’s any convention on level numbers?

For example, would a typical house with 2 floors and a basement be
0, 1, 2 or -1, 0, 1 or -1, 1, 2 or maybe even B, 1, 2.

I know the system provides flexibility, but I don’t really care what I do and would rather follow whatever scheme the developers had in mind – particularly as the release announcement made a big point of saying that this was added with further assistant integrations in mind.

The docs suggest negative numbers for “underground floors”, so I’ve been assuming the ground floor was zero.