First, they have memorized the way you wrote the number. It's easy to tell with your pencil stroke what number you wrote. Then, they intend to write the number that they can magically see in the eye of their mind with the ordinary pencil as you write your own. A mentalist will ask the viewer to focus on a set of numbers (such as their phone number).
The mentalist will then ask the viewer to repeat the numbers in their head to add drama and emphasis. There are two sides to the way mentalists guess numbers. These are through complete deception. Or by reading body language.
Number guessing tricks include the Swami Gimmick, simple math tricks or by using other clever mentalism tricks. Whereas to guess someone's PIN number, this can be achieved by non-verbal cues. If you want to know how mentalists read minds or how mentalists guess numbers, all you need to do is keep reading. If you have more questions about mentalism or magic, I'll try to answer them (or specifically how mentalists guess numbers), please comment below with your questions.
Mentalists don't have superpowers the way they want us to believe, and from the above excerpt, it's very obvious that they are intelligent and have some skills that any normal person would first need to train and acquire before they can do what mentalists do. Master Mentalism is an in-depth course that will show you the secrets behind most of the popular mentalist magic tricks out there. If you want to learn how to do incredible mentalist tricks that will make your friend gawk, check out the Master Mentalism course. When the mentalist asks him to repeat the number chosen in his mind, he gives the illusion that the mentalist is reading the person's mind.