What does the red dot and black circle on the edge of Feng Shui compass mean?

What does the red dot and black circle beside the geomantic compass mean? -There are two kinds of red spots and black spots. 1. Red dots and black dots exist when gold is divided according to the degree of the 28th night line. Second, according to the 64 hexagrams of the ternary disk, there are 384 red dots and black dots. Third, there are two layers of such red spots and black spots on the comprehensive disk, namely, the red spots and black spots on the August line and the red spots and black spots at 384 meters. That is, red dots are available lines and black dots are unavailable lines, but they must be used flexibly according to the surrounding mountainous terrain. There used to be a master who taught his disciples to use a compass, but his cultural quality was so poor that the compass could not explain the church clearly. The easiest way is to use a red line instead of a black line and surround the whole church in a few minutes.