New Guy In Prison

After a meal convicts are waiting to go back to their cells and someone shouts out "47" and a lot of cons laugh. Another shouts "29" and gets more laughs. The new guy says "what's up? and another con explains that all the jokes have ben told so many times that we gave them all numbers. The new guy calls out a number and no one laughs. He tries another and still no laughs. So he tries a number that he's already heard and no laughs again. "What gives?", he says to the guy who explained the system. The guy shrugs and says," Some people can tell a joke and some can't.