Count up how many people guessed correctly. Or fudge it if you're tired of waiting around for enough people to sign in to make the count. There's sixteen people in this workshop in theory so if it's eight or less, you're doing a pretty good job for a beginner; grab yourself a t-shirt from the box to the left of the table. If it's more than eight, you probably need some more practice, so while you're working on that, grab a t-shirt from the box to the right of the table to help you lull people into a false sense of security.