In packing problems, the idea is to minimize unused space. Our local garage (the same one that had the confusing sign) has decided to utilize this idea by making use of space that would otherwise be wasted. At the end of each aisle and right by the stairs they have special spots for compact cars:

You might think that 70 inches [178 cm] is too small for a car — a web search revealed that parking spots should be 96 inches (8 feet or 244 cm) to 108 inches (9 feet or 274 cm). But that would actually give you room to open the doors, and most of the time the doors are closed. If you look at the width of a Toyota Corolla, for example, it’s only 69.3 inches wide, which allows a whole 0.7 inches (1.8 cm) of leeway for maneuvering into this empty spot! And since these special parking spaces are always on the end of a row, presumably the driver can, umm, scoot across the front and get out on the passenger side.

Our garages: when they say “compact”, they mean it.