What do the eight evil spirits in the yellow calendar mean?

There are eight evil spirits in geomantic omen, which refer to the direction of incoming water, such as the direction of Geng Ding. If you accept Kun's word for water, you will commit eight evils.

Similarly, Xiang Kun can't get water from Geng Ding.

Others, such as: don't drink water from ethylene propylene, don't drink water from ethylene propylene. Ren Xinji is dry to water, and Ren Xinji is dry to water.