Suppose you own a valet parking service in a long, narrow alley, so the vehicles are all parked parallel-parking style. Some of your customers drive cars and use only 1 space. Others drive stretch limos and require 2 spaces. One way of parking the vehicles would be to assign 2 spaces to each vehicle, regardless of size. Your claim tickets would say "Vehicle is parked starting in space 0 (maximum vehicle size is 2 spaces)" or "starting in space 2", or "starting in space 4", etc.
This would work, but it wastes spaces because you are reserving 2 spaces for cars which need only 1. So instead, you pack the vehicles together, with cars taking only one space and limos taking two. Your employees know that car takes only one space, so if a ticket says "starting in space 1 (maximum vehicle size is 2 spaces)" they know that "The car is in space 1, and space 2 belongs to somebody else." The car's space 2 actually overlaps the limo parked in spaces 2 and 3, but it would be a bad idea to use it or you're going to dent the limo.