What does the iron mirror mean by grinding the full moon again?

Re-grinding of iron mirror: Fortune teller said that the bronze mirror will be blurred after it is permanent, the old bronze mirror needs to be re-ground, and the re-ground bronze mirror will be as bright as new.

The moon is round: the moon is round and the light shines all over the sky.

It is often used in divination that "the old mirror is reground and the moon is round", which means that fate shines like the old bronze mirror after regrinding. Without haze, it would be like a bright full moon. In short, it will be lucky.