Sprwt walks through the cart line by line, only touching ordering systems ticked under Allow on:

• Percentage coupons take the percentage off each eligible line (excluded meals are skipped for that coupon).
• Fixed amount coupons take the amount off progressively — the first eligible line absorbs as much as it can, the remainder carries to the next line, until the full amount is used up. The discount can never exceed the subtotal.
• If a Dynamic Custom Rate tier was selected, its value is used instead of the base Value.
• The wallet types do not change the total at all.

If a coupon's Discount Applied to Delivery Fee? is on, the delivery fee is discounted as well; with Offer Free Delivery? the fee is removed for the allowed ordering systems.