What is an example of symbolism in the novel, Al Capone Does My Homework?

Piper throws a baseball into rec yard with a note asking Capone to sign it, intending to sell the ball and pay back the money she owes from buying gifts with counterfeit money. Capone, however, throws the ball back with the words “Do your own time” (201) scratched on it. This baseball symbolizes how the inmates learn and use information from the outside.