What is pinching your fingers when telling fortune? What are you talking about?

According to experts, the joints of fingers can correspond to ten heavenly stems, twelve earthly branches and sixty jiazi. There are many schools of fortune telling. Pinching your fingers is just convenient for memory. Generally speaking, it is to pinch the thumb of the left hand. Some fortune-telling techniques, such as Daoism, are too complicated. For example, nine planets is a dragon walker, and it is possible to arrange the heavens and the earth in his hand. Not everyone carries a pen and paper with them, and it is most convenient to hold their fingers in their hands. Most fortune tellers look at heavenly stems and earthly branches and so on. By the way, if fortune telling is superstitious, why is it handed down in China?