Well, let's assume I have written and circled 29 on my paper, and I only reveal to you in a normal and sensory way (for example, on this forum) that I have written one of the thirty numbers: 1, 2, 3, 4, ..., 28, 29, 30.
Suppose you tell me (correctly): "You wrote and circled '29' ". This would be a rather extraordinary feat, which "proves" telepathy in a much more convincing way than if you just guessed right in a four-possibility test, with a 25% chance of getting it right from pure chance alone.