It seems like everytime I train at the gym I get this question.
Today it was while I was doing single arm machine preacher curls, The guy using the dip machine looks me over, and says "how much can you do?" I replied "I have no idea" which absolutely blew his mind. He said what do you mean you don't know, I said what does it matter? He just stared at me, so I had to explain that I'm not a weightlifter, powerlifter or strong man, that I train to build my body. Anyhow it led to more wasted time trying to get this clown to understand...