A convict stands up in the prison mess hall and yells, “Seventy-three!”
All the other inmates laugh. A new prisoner asks a guard what’s going on. The guard explains that the prison has one joke book and all the prisoners have memorized it. So instead of telling the joke, they just say the number of it. So the new prisoner stands up and yells, “Forty-eight!”
He gets no response and asks the guard why. The guard says to him, “Some guys know how to tell ’em, some guys don’t.”