Let's say you have 2 variants for each of your product.
Overall, you can see that the discount will be apply only on the (Basic) variant of the product called here "Top Discounts".
You go inside the Automatic Discount app and create a new discount rule using your previously created discount code. Then you can use 2 different approaches for the discount rule:
(if $6 or less inside the cart).
(if 1 item or more inside the cart)
The difference between a % discount and a $ discount is the ability to limit the $ discount to only apply once per order. So, for example, here we will limit to once per order the $6 discount, no matter how many "Basic" products you have inside the shopping cart.
You can also NOT trigger the discount if there is one or more other products (or variants) in the cart.