That didn't work how he expected, but it was still a correct guess, so who cares, sure, he meant to do that. It doesn't matter, as long as he wins. Which is more about his pride than anything else, the terms of this absurd wager are pretty meaningless. Of course Johnny's losing condition was poorly thought out and completely open ended, which was incredibly foolish, but even his winning condition is...unambitious. And ambiguous. "'U.'" The letter, not the beginning of some pronouncement.