What does the sentence written by Gan Long mean?

Puyi said that he had found a personal letter from Emperor Qianlong, which mentioned that Yongzheng had killed his brother in order to compete for the throne, and also had the language of repentance for his father, but Puyi did not elaborate on the content.

One day, Puyi and Pu Jie came to the West Chamber Buddhist Temple in hall of mental cultivation and found a package wrapped in red paper in the niche, which suddenly aroused the curiosity of the two brothers. Out of curiosity, the two brothers climbed up and took the red package. As soon as they got it, they saw a sentence written on the surface of the parcel: "Whoever drives it is not my descendant."

After opening it, I found that it was a handwritten testament of Emperor Qianlong. The imperial edict states in detail that when Yong Zhengdi was alive, he killed his younger brother in order to compete for the throne. In order to cover up the past for Yongzheng, Emperor Qianlong wrote a confession to his father and put it in a Buddhist shrine.

What he did was that Emperor Qianlong prayed to the Buddha from the heart, which was written by Emperor Qianlong with a feeling of atoning for his father. Emperor Qianlong didn't want others to know these things about his father, so he wrote the words who opened it and who wasn't my son on the red paper package.

Extended information The truth of Yongzheng's succession:

There are many rumors about Yong Zhengdi's impropriety among the people. Many people say that Kangxi's original wish was to pass on the throne to his fourteen sons, but the fourth son, Yin Zhen, tampered with it and then ascended the throne. Later, after Puyi and Pu Jie discovered the love of Qianlong's testamentary edict, they realized that Yong Zhengdi's improper position was a fabricated lie. Because, for such a big thing as succession, it is impossible to write an imperial edict without Manchu. It is obvious that the story of fourteen sons changing into four sons is spread out of thin air.