So this guy calls the pizza shop. "How many sizes of pizza do you sell?" he asks.
"Three," says the clerk, "small, medium, and large."
"How many pieces are there in each one?" asks the caller.
"The small pizza has four pieces, the medium pizza has eight pieces, and the large pizza has twelve pieces," replies the clerk.
The caller is silent for a long pause. Finally he asks, "Can I order a large pizza, and have you just cut it into eight pieces instead of twelve?"
The clerk is by now running short of patience. "Sure, buddy, whatever you like, we can do. What's the deal with eight pieces instead of twelve?"
"Well, I think I want more than a medium pizza, but I'm not sure I can eat twelve slices if I get a large so I figured it would be better to just cut it into eight."