This is a numerology formula in ancient China, which means: people born in Guishui (the god and the devil used in the ancient Tiangong map) in Mitsuki (in April of the lunar calendar) can use Geng Jin (one of the twelve earthly branches in the ancient Tiangong map) if there is no Jin Xin; Ding Huo (one of the twelve heavenly stems in ancient Chinese characters) is forbidden to destroy the pattern. This situation can be avoided if there is Renshui (one of the twelve dry days in the ancient eight characters).
Simply put, this sentence means: People born in Mitsuki can use Geng Jin if they don't have Jin Xin, but they are afraid of Ding Huo. If they have water, it can help to resolve the adverse effects. However, it should be noted that this is just a traditional numerology view, which has no scientific basis and is for reference only.