On the product page (advanced / Inventory tab), the field is : Allowed quantities As per the hint: Enter a comma separated list of quantities you want this product to be restricted to. Instead of a quantity textbox that allows them to enter any quantity, they will receive a dropdown list of the values you enter here.
On the product page (advanced / Inventory tab), the field is : Allowed quantities As per the hint: Enter a comma separated list of quantities you want this product to be restricted to. Instead of a quantity textbox that allows them to enter any quantity, they will receive a dropdown list of the values you enter here.