1. polina_lapteva says:

I can explain the numbers for you. The answer below says about dashes, but it actually counts the number of corners.
So, 1 – one angle between the vertical and forty-five-degree stick, 2-the angle at the bottom and on the part that is currently drawn rounded, 3 – 3 angles ~45 degrees (one “looks” to the left, another to the right, the third again to the left), and 4 – three angles in the triangle and the fourth external (the dash that is on the right does not count).

2. logik_logik says:

We live in a world where there are elementary, simple things, we perceive them as certain axioms that do not need to be proved. Here is a spoon that does not need to be understood, but the difference between spoons needs to be understood, as well as the difference in numbers and letters.

3. d says:

Pure convention, which is obvious from the existence of other languages. It just happened that way historically. Anything can be labeled as anything, there is no internal connection between the symbol and what it means (for example, between the word “spoon” and the spoon with which you eat soup). This connection appears only in our brain when we begin to understand that the sounds forming the word “spoon” are somehow connected with the object on which we are served food.