In the case of this test, 0% means you're defeating the prediction algorithm. 50% means (if you're predicting their prediction) means you're achieving random.

In the case of this test, 0% means you're defeating the prediction algorithm. 50% means (if you're predicting their prediction) means you're achieving random. "Free will" is a bit strong, it's more about whether people can produce randomness, which they generally can't.