You think that's bad, you should try working out Scottish tenement flat numbering.
Your guess whether 1/6 is Flat 1 at No.6 or Flat 6 at No. 1. Or flat 6 on the first floor (or the ground floor) and the building doesn't have a number. Or whether 21/2 is Flat 2 at No. 21, Flat 21 at No. 2, or the first flat on the second floor at No. 2, or the second flat on the first floor at No. 2. Or 2-and-a-half (which is likely to be at the rear of the building) and there isn't a flat number. Or there is a flat number but you don't know it.
Or in Edinburgh, where everything's Listed, the name of the person living in the flat in 1850 because the door bell-pulls haven't been re- engraved since then.
Owain