I think you misunderstood. Fred is suggesting that Mark is smart for cashing out at $37 because the price is now $31. He also thinks that if Mark buys stock at $31 that will be a strong enough signal to send the price to $45. That seems a bit of a stretch to me but it's just a hypothetical situation, not a statement of fact.
Yes, he sold at $37.58 than price moves up, than 31$ and for markets news, that he bought shares at 31 back, can possibly be a big catalyst for growth. That's just a joke, i suppose this was not his purpose, but this "move" could be a big biz.