Help with promotion

Hi guys

I want to setup a promo code promotion on my store and I dont know how to set the conditions for it.

Specifically I will be selling rugs and I want to give out 1 free padding per customer.



However I have 4 different padding sizes and I can only give 1 free per customer per order.



While I saw how to set the condition so that the code can only be used once per customer, I dont know how to set the condition so if 2 paddings are placed in the cart only 1 will be free.



Using the condition “product in” will make all the paddings in the cart free after promo code.



Can someone help me to set this up?