BIG BALES, LITTLE BALES

When is a bale not a bale?

Or put it this way, when is an 8 by 4 by 4 bale not an 8x4x4 bale - when its 7 x 4 x 4.


Apparently some farmers are squeezing more bales onto trailers, but forgetting to let buyers know that they are getting that little bit less.

Is there a word for this?