EAN-13 barcode, how is the 13th digit formed?

Question

Barcodes

Actually the Wikipedia article itself https://ru.wikipedia.org/wiki/European_Article_Number
There is a table in the section on the internal structure of the EAN-13 code, but it is still not clear how the 13th digit is calculated (the first in order on the barcode).
Can someone explain in more detail.

Answer 1

What exactly do you not understand? 13th figure is determined by the sequence of L- and G-codes of the left side (numbers 12-7).

Answer 2

Somehow Russian is a bit contrary to English. https://en.wikipedia.org/wiki/International_Articl...
The English version says that the first 3 digits are the country code, https://en.wikipedia.org/wiki/List_of_GS1_country_codes