The cities refer to the orientation of the box, not the size(usually used with full apples though).
In Canada we call them 1's, 2's and 3's (lay the box flat, put it on its side, or stand it on end)
The corresponding cities are LA, Las Vegas and New York.
So if a DP asks for a full apple New York, you know to stand it up tallways.
Also heard Chicago being used intead of Las Vegas