Why is it called the 16th Sect, the 27th are the same, the 38th are friends, and the 49th are friends? How do you explain it?

This is a question in the I Ching. Judging from the patterns in the "River Diagram", it is "the sky generates water, and the earth generates 60% of it" (1 and 6 are both in the north, so it is called the *** sect); "2nd of the earth generates fire, and the sky generates 70% of it" (2. , Seven are together in the south, they are called Tongdao); "Three in the sky produce wood, and eighty percent of it is in the earth" (Three and eight are in the east together, they are called friends); "Fourths in the earth produce gold, and ninety percent of it are in the sky" (four and nine are in the west together , called as a friend).