Where I work, rooms on the 1st floor have numbers like 1.01, 1.02 etc., on the ground floor it's 0.01, 0.02 etc., and in the basement it's -1.01, -1.02 etc. Th

Where I work, rooms on the 1st floor have numbers like 1.01, 1.02 etc., on the ground floor it's 0.01, 0.02 etc., and in the basement it's -1.01, -1.02 etc. This is confusing for some people (unfamiliar with the situation), who need to go to a number in the basement but consistently turn up two floors higher.