I'll be back in 5 rices.

Today I went to the restaurant next door to order take-out. I gave them my order and then said "Ok, I'll be back in 5 minutes" so that I could run to the market and pick up a few things. When I returned, the waitresses looked at me kind of funny and one of them held up her hand with all fingers outstretched and said "5 minutes?!" sort of incredulously. Was she judging me on how long I took? I thought I took exactly 5 minutes. Why so shocked? I said "Yes, I came back in 5 minutes." Then all of the waitresses busted out laughing. Turns out they thought I wanted 5 orders of rice when I said I would be back in 5 minutes. One of the waitresses bolted for the kitchen to correct my order. When I said "wu fen" for 5 minutes, it sounded like "wu fan" for 5 rice...at least I think that was the confusion. Adventures in language.