If you refuse to tell them which finger you used, and comply by only pressing whichever finger they ask you to press, they will have a 10% chance of getting in

If you refuse to tell them which finger you used, and comply by only pressing whichever finger they ask you to press, they will have a 10% chance of getting in each time. So if you chose only 1 finger and you chose it randomly, they will have a 50% chance of getting in after 5 attempts.