Shipping document classification

I’ve been asked a question on shipping documents and the need to have clear and correct description of goods.
For example men’s footwear, 80% leather, 20% polyurethane.
What criteria would we need to use to calculate this?
Is it by weight, area, value?
Any guidance would be much appreciated.

I would clarify the type of footwear - Sport, Formal etc… and breakdown what the upper is made of and the sole.