Pithy formula and interpretation of common cable selection

In our daily sales, we may encounter customers asking about ACSR Cable selection in the process of maintenance and repair. As a cable salesman, choosing the right cable for customers is the top priority of this work.
First, the actual power of the load should be considered, at the same time, the maximum current to be borne by the cable should be calculated, and then the appropriate cable should be selected. The following is the relevant contents sorted out by the editor in AAAC Cable treasure. I hope I can provide some help for my colleagues.

[doggerel]: five out of ten, two out of one hundred, fifty-three out of four, and 75% off for buried casing.
[explanation]: according to the total current required by the insulated conductor, when the total current is less than 10a, the cross-sectional area of the conductor per square millimeter can pass 5A current, if it is more than 100A, it can only pass 2A current per square millimeter, 4A current per square millimeter between 10 ~ 50A and 3a current per square millimeter between 50 ~ 100A. After this calculation, In case of buried or casing laying, the current value that can be passed shall be multiplied by 0.75.
The calculation method given above obtains the allowable current per square millimeter. The selection of the actual specific conductor section should be: first determine the current required by the electrical equipment (including rated current and appropriate margin), then compare the current range in the doggerel according to the required current value, and then the conductor section that should be selected can be obtained by “allowable current per square millimeter” belonging to the range at the required current value.

For example, the rated current of an electrical equipment is 20A. Considering a certain margin, the required current is determined to be 22a. Then, find out that the current range of 22a current in the above doggerel belongs to 10 ~ 50a, and the available current per square millimeter is 4a. Finally, divide 22a by 4a to obtain the conductor section s that should be selected as:
S = 22 / 4 = 5.5 (mm2). According to this value, the conductor with corresponding section can be selected. If the calculated sectional area is not in the conductor section specification series, a slightly larger conductor section can be selected.