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?

They're labelling a lift "floors 2 to 4" on a floor which isn't in the interval [2...4]?

Well, yes; they're telling you what floors it'll take you to other than the one you're currently on. That may be mathematically dodgy but common-sense-wise it's perfectly reasonable!

Oh right, I see. So the lift for 2-4 has a door on the car park floor, and it takes you up to 2, 3 and 4, and the lift for -1-2 takes you to the basement, ground floor, 1 and 2, one of which is the floor you're already on in the car park. Shops are taller than car parks, so I suppose the bottom layer of shops covers floors G and 1, and the top layer of shops is floors 2 and 3 and possibly 4. So if you know you want to go to the top layer of shops or car park levels 3 and 4 you get in that lift right there without having to pootle about with people who are going to the bottom floors, and if you are going to the bottom floor to work your way up you are assumed to be Slow and therefore can share your lift with the people who got the bus or parked on floors G and 1 and the basement.