How to Make Coupon Apply to Multiples of the Same Product

Hi,

A coupon applies to the whole cart, not to a product.
So if you set a fixed value it in, it's for the whole cart.
Similarily if you set a percentage value, it's for the whole cart.
Also, if you activate also the "Coupon percentage applies to product only" setting of the coupon, then the percentage value of the coupon will only apply on the products for which the coupon is restricted with the products/categories settings.
So suppose that your product costs $50. You could configure your coupon to be 10% with that "Coupon percentage applies to product only" setting activated and the coupon restricted to your product.
That way, if you had 1 quantity of that product in the cart, the coupon would give you $5. If you had 2 quantity of it, it would give you $10, etc, and other products in the cart wouldn't be taken into account.