Cart Price Rules overwrites Customer product price group
On our webshop we have a Customer Product Price Groups of 10% discount. Now I wanna do a Cart Price Rules with 20%. When I fill in this rule the checkout count like 10% discount + 20% discount. I would like to have it in total 20% so that the Cart Price Rules overwrite the Customer Product Price Groups.
Also when I have a special product on sale like 25% discount then the Cart Price Rules of 20% goes extra off. I would like to have that the 25% stays on the sale product.