Tenth

A man tells his story of how little things can have a big impact. One night, he's working late at a dry cleaners when a woman and her son come to pick up their cleaning. He lets them in; the boy has a baseball glove and sits looking sad while his mother gets her clothes for a flight she says she's taking the next day to L.A. They leave and the clerk sees that the boy has forgotten his glove. In the morning, he decides to take the subway to return it to the boy. What's the tenth?