What does the fortune teller mean when he says there is red sand under a girl?

This is a fallacy in the ancient fortune-telling world, which was used by those malicious fortune-tellers to confuse the people and want to collect money to eat girl tofu. Red sand is the evil spirit of the body, which means that any woman who orders Meng Yue to be born on the Unitary Day, born on the fourth day in the middle, and born on the ugly day in a quarter of a month is a woman with red sand below. What is red sand? Get married when you have your period. In ancient times, it was considered unlucky to get married during menstruation. So the fortune teller used this hype to scare girls, saying that "one woman marries three families" is scary enough, right? A clever girl said, then I'm not stupid enough to get married by menstruation, am I? The fortune teller said that the female killer Hongsha would get married in disorder! So what should we do? You must come and beg me to choose an auspicious day when you get married, right? Remember, there is a charge, and remember that you want me to draw a cinnabar symbol for you. I can't do this thing for free, and I can't draw it. This deceptive trick was exposed in ancient times. The imperial edict abolished this red sand, and now some people cheat people with it?