All welcome. Faced with the problem. May be someone will prompt. The bottom line is this:
In the item card, you must implement the following functionality: to allow the user to specify the number for each dimension (attribute of product). For example like on this site (no ads) - https://prostotekstil.ru/futbolka-tuman-4326
. For each size the quantity of goods, when you add to cart all natural is considered as a separate item since the original item is grouped and consists of goods with different sizes of the same model sold clothes.