Use a Product % Discount campaign (supported alternative)

Create an Advanced Discount Code campaign that uses a Product Discount module (percentage off) applied to the selected products or variants — this is supported. Note: this will apply to the product price field as supported by the module. Because Discounty cannot issue custom discount codes and applying specifically to the 'compare-at' price is not supported/clear, consider either (a) adjusting your product pricing fields so the intended price is the price field the discount will reduce, or (b) using Shopify's native discount code functionality (outside Discounty) which may better support codes and price targeting.