Umbrella Sam (played by Shemp Howard) is asked why he walks around with an umbrella when it is sunny. He says "I don't know. I'm a Damon Runyon character." The movie is based on the story "Princess O'Hara" by Runyon.
How should I know... I'm a Damon Runyon character!
When Grover places his $100 bet, he places it on Tea Biscuit's entered number. However, the horse with that number didn't win, so the ticket is worthless. Never mind that Tea Biscuit won the race; bets at the track are on numbers, not on names.