how does willy contradict himself in the advice he gives biff as he goes to see bill oliver ? how do you explain this contradiction?

He tells them to wear a business suit, talk as little as possible, don't make jokes, walk in seriously, ask for fifteen thousand dollars, don't say, "Gee," walk in with a big laugh and tell a couple of stories to lighten things up, and that personality wins the day. The contradictions are that Biff is not supposed to talk much, but he is supposed to start out with a couple of stories. He is to be serious and not joke, yet he is supposed to "lighten things up."