What are the allusions to the three steles embedded in the back porch wall of Jia Qian Building in Nanjing Presidential Palace? What is the value in calligraphy art?

This monument is called "Tianfa Oracle Monument", which was the "Tianxi Monument" in Sun Hao during the Three Kingdoms period. Because it was found to have been broken into three sections, it is also called "three-section monument". The font on the tablet is a transitional body from seal script to official script, which is called "hanging body". His brushwork is simple and elegant, which is of great value to the study of China's calligraphy.