In the sixth year of Yongzheng, when he was reading the secret letter, he sent someone to send a secret letter to get all the characters he wanted. Later, Yue Zhongqi wrote the eight characters of his important generals into the secret book. At that time, Yongzheng personally told their fortune. If these people's horoscopes are not good, he may not reuse these people. Although numerology is illusory, people who believe will always believe it, so Yongzheng will refer to the birthday when playing tricks on people.
This is also a means to close the relationship between him and the minister, because Yongzheng is more concerned about his cronies. He can show them eight characters to see what disasters they will have, or some diseases. I think in this way, Yongzheng feels more comfortable in employing people, because he can see whose life is better, or it is better to arrange someone to do something. So when he is in office, he is more dependent on his birthday.
I think Yongzheng's interest is also relatively grounded. Although he is the son of heaven, it does not mean that his hobbies must be hunting piano, chess, calligraphy and painting. I think he actually knows the whole world through numerology. But in this case, it is also possible to be deceived by some ministers with ulterior motives, because such things as eight characters can be fabricated.