Translate uncommon words, who can explain this sentence?

Yi: Onomatopoeia, which describes the sound of horseshoes stepping on the ground.

Bu: The ancients were superstitious and burned tortoise shells, thinking that good and evil could be inferred from the burning cracks.

Fear: the ancient word "Yue".

Even number: even number.

Technetium: Radioactive element, the first artificial elements, is a good superconductor.

Xu: In ancient times, odd numbers were called "Xu" when they were sandwiched between fingers.

Between the fingers: "Strange as a leap."

remainder

To sum up, this "why" means:

The ancients used the sound of the horse's front hoof to divine the radioactive element "technetium" by burning tortoise shells, and looked at the number of cracks burned and the number of times the horse's front hoof landed to get good or bad luck. If the sum of the two is divisible by 2, it means good luck, and if there is a remainder, it means bad luck. Why?