I went to tell my fortune the other day. How does the fortune teller know my last name?

Oh, hehe, this is a card game. I have seen other people's calculations in street stalls before, and I didn't understand them at that time. Until one time, when I was eating Dongdong in KFC, KFC gave me a set of small cards for guessing numbers, such as 1- 10,1-20,21-30,365438+. So, there is nothing magical, just a little skill.