What does this joke mean? Please indicate the satisfaction score.

Four days ago, this man's wine was stolen by others. His friend asked him to write down the word "urine pain" so that no one would steal the wine in the barrel. I didn't know that others would pee directly in it when they saw the word "painful urination", so the bucket was full on the fifth day. . So the last bit of wine was ruined ~ so he cried. . . . . . . .