It's bad bad bad math. Or rather a shift of perspective.
If the bellboy keeps 2pounds (don't have the sign on my laptop), that leaves 28 pounds left. 28 divided by 3 isn't 9, it's 9.33333333333recurring so there is no missing pound.
Nathaniel threw a hissy fit because he didn't like the way the problem was presented and I told him science was better than philosophy for these kind of problems. :P