After all your balls are exhausted the number game comes up. Look for the number at the top left corner of the digital screen. Before R2-D2 lands, press the flipper buttons simultaneusly as many times as 1/10 of the number. (Example: the number is 70, press the buttons simultaneusly 7 times.) When R2-D2 comes down, the number should be the same. You earned a free credit!