How to crack the crystal ball mind reading?

Cracking the gypsy crystal ball mind reading test

In fact, every subtracted two-digit number can be expressed by an algebraic expression, that is, 10X+Y-(X+Y)=9X.

So all the numbers you subtract are multiples of 9, and each multiple of 9 corresponds to one in his chart.

The same. As for each pattern, it is different, because every time it is measured, it is a multiple of 9.

The case has to be changed once. Moreover, when you count casually like a crystal ball (excluding multiples of 9)

This is not allowed because it is not a multiple of 9.

You got it?