Promotion / discount

Can someone explain how does the promotion or discounts work in cs-cart.



Scenario:


  1. I got a promotion where customer in checkout enters CODE and received say 10%.



    BUT



    some products got Price (20$) and [I]List price/I already with say 20% discount. Some or even same may got quantity order discount say if ordered 10+ price would be 18$.



    Does the “stop other rules” stop the promotion from giving discount to product described above? If no how to avoid discount on discount on discount?



    Thank you