What does it mean to watch Go at the Hongmen Banquet?

In ancient Weiqi, the chessboard was divided into four pieces: flat, up, down and forward. In ancient Weiqi, "Ping" refers to the lower left corner, "Shang" refers to the upper left corner, "Qu" refers to the upper right corner and "Jin" refers to the lower right corner. For example, Sanjiu Road means three lines in horizontal direction and nine lines in vertical direction. There is a detailed introduction in Zi Si Pu of Ling.