What problem concerning the list of invited guests does the servant have?

The servant in Act 1 Scene 2 of Shakespeare's Romeo and Juliet has been given a list of people to invite to Capulet's "old accustomed feast". Unfortunately he cannot read, and so does not know who to deliver the invitations to. He asks Romeo to read it for him, and thus Romeo finds out that Rosaline is invited to the party. This makes him want to crash it.