I'm not sure what they *did* mean. I would have assumed the sign would have been written by a human. But it sounds like the sort of snafu that could only have come out of software. If the signs are automatically produced it could make sense (-1 is a placeholder, -1 means floor -1 but the ordering is screwed up, etc). But I'm sure I'm missing something.

For all I know, it's like HP Staion 9 3/4 or Being John Malkovich floor 7 1/2, and if you'd been able to get in you'd have been whisked to the top floor *the day before*.