Given that I've never heard the term "hundredweight" before, I'd say not much. Like "stone," it's just not used on this side of the pond.

I am surprised that you do not see the problem given your background as a mathematician. A US pint is 16 ounces - a UK pint is 20 ounces. I am a UK resident ordering something from a US distributer that is sold in pints. The problem is fairly obvious....