Haaang on. They're labelling a lift "floors 2 to 4" on a floor which isn't in the interval [2...4]? But it is in the interval [-1...2]?

So, floor 2 is the first floor of carpark? And therefore the default ingress to the arcade. So clearly you label everything with reference to floor 2. I think these signs [2...4] and [-1...2] (ok, [2...-1]) ought to be installed on level 2. But then clearly lift [2...4] ought not to be instantiated on the ground floor.

What happens in -1?