Why do fortune tellers know how many people there are in other people's families?

Hehe, I know he really didn't guess, but he does know that there are two ways, that is, from the eight characters on the six hexagram or the face of the hand. As long as he is proficient, it is a piece of cake. The other is to see incense, and others have fairy houses at home. People already knew what you were going to do before you went. I've seen them all.