Of course, each mantissa is represented by ten numbers from 0 to 9.

The key lies in the previous figures. Don't just represent the floor.

If you are on the first floor, 10 1, 102 is easy to remember, but outsiders can easily guess.

Nowadays, the method used by many hotels is to add a math before the number.

For example, the first floor can be set to 1 10 1, 1 102 and so on. This is not easy to guess.