Why can six-hexagram divination predict the future, and all of them are invalid?

I give an answer based on experience, but there may be mistakes. You need to judge by yourself and use strict logical reasoning, just like a person with good grades and usually modest will take the TEM4 exam tomorrow, so it is inferred that the probability of his passing is almost 100%. Or someone is getting married. Under normal circumstances, it can be inferred that he will break the money recently (spent100000 left).