If I have 20/20 vision, that broadly means I can see at 20 feet what the average person can see at 20 feet.
Example : you have 3 cards, A B and C. There is several ways to order them.
ABC - ACB - BCA - BAC - CAB - CBA
Six are possibles, because the answer is "3!", factoriel 3, 3x2x1=6. And you have 1 chance in 6 to guess the position of cards.
You can use factoriels to know how many chance you have to win in games like lottery, loto... (not a lot !).
Glad I'm not alone not knowing what Bolt's record was