What does "the ninth day, the second day and the third day ..." mean in Zhouyi?

According to Zhu's explanation, the basic steps are "four camps", that is, "one divides into two", "hanging one", "four" and "returning to the strange". The so-called split into two is to randomly divide forty-nine yarrow trees into two piles; Hanging one is to take one from the left pile and put it between the fingers of the left hand; Step 4, count the left and right piles of yarrow in groups of four; To return to seven is to merge the remaining "odd" in the two piles (the last four are enough for a group) and add the one that hangs one, so that the result is either five or nine, which is called "one change". After the first change, remove 59, mix the remaining 40 or 40 yarrows together, and then carry out the "second change" and "third change" according to the above method, and the result is either four or eight. After three changes, the sum above is subtracted, and the remaining numbers are thirty-six, thirty-two, twenty-eight, twenty-four, and then divided by four to get the four numbers of nine, eight, seven and six respectively. Nine is Lao Yang, eight is Shaoyin, seven is Shaoyang, and six is Laoyin. This is the so-called "crossing method" In ancient times, there was a kind of divination, which was called "breaking the yarrow" method. The method and process are described in detail in the river map ... 1. Deduct 49 yarrow. 49 yarrow tied with Artest Chi. 2.49 yarrow trees were randomly separated. Split in two. Tai Chi gave birth to two kinds of instruments. 4. The number of four yarrow roots on the right and left hand indicates that there are four seasons in a year. It also means four elephants. 5. The number of roots and remaining roots of the four yarrows on the left and right hands is called a leap every three years and a leap every five years. It is important to emphasize the leap again after five years. After 6 and 3 times, the result is 24. Divide by 4 to get 6, which means old yin changes. 7, the result is 28, indicating that shaoyang remains unchanged, and 8, the result is 32, indicating that shaoyin remains unchanged. 9, the result is 36, indicating that Lao Yang has changed. 10, the middle 10 and 5 are multiplied to get 50, and only 49 yarrows are used. The river map is a picture about the divination process. Modern people will understand its ancient divination method as long as they see the river map.