When calculating product discounts, if the product is a specified product, apply a $20 discount to the product's sell price. From the Conditional Actions admin page (/admin/store/ca):
  1. Select the Add a predicate tab
  2. Set the following fields
  3. Click the Save predicate button
  4. Set the following fields
  5. Click the Add condition button
  6. Set the following fields
  7. Click the Save changes button
  8. Select the Actions tab
  9. Set the following fields
  10. Click the Add action button
  11. Set the following fields
  12. Select the Save changes button
Congratulations, you have completed setting up a $20 Product Specific Discount. The discount should be reflected in the products Sell Price on the product, cart, checkout and review pages as well as on the invoice. You may need to clear Drupal's cache before the changes visible.