Hi,
The percentage amount will be taken off of the products linked to the coupon. And same with the restrictions. If you restrict the coupon to a product and with a minimum amount and a minimum quantity, it's the minimum amount and minimum quantity of that product in the cart which are checked.
I think that what you want to do is to not restrict the coupon to that product, and instead of entering 100% for the discount value, use the flat amount" field to enter the price of that product. That way, the restrictions on the amount and quantity of the coupon will apply to the whole cart, and the discount amount applied by the coupon will be the same value as the price of the product.