Not only that but which floor is the 13th (in the West) or 14th (in China)? Often those numbers are skipped because "luck", "feng shui", or other superstitious nonsense.

Do you count the machine floors in high rise buildings?

In AU, the ground floor is effectively "zero", the first floor is the one above ground. Depending on the design of the building, there might be a "mezzanine" floor between ground and 1st.

Basements usually follow the same pattern, so B1 is the first floor below ground etc.