It sounds like you're trying to create a shopping cart promotion rule based on specific SKUs. To achieve your desired outcome, you need to configure your rule with the following conditions and actions:
Under "Apply the rule only to cart items matching the following conditions", select "SKU is one of" and enter the list of SKUs you want to include.
Under "Apply", select "Percent of product price discount" and set the discount amount to 10% (assuming each of the SKUs is priced at $10).
Under "Discount Amount", set "Maximum Qty Discount is Applied To" to "2".
Under "Apply the rule only to cart items matching the following conditions (leave blank for all items)", select "Total quantity greater than or equal to" and set the quantity to "20".
This rule will apply a 10% discount to each SKU in the list when the cart quantity of those SKUs is 20 or more, and limit the discount to a maximum of 2 per SKU.
By configuring the rule this way, it should only apply the discount to the specific SKUs you want, and exclude any other SKUs that are not included in the list.