I'm confused on what you're saying. I've been told to never do a rain check on "as advertised" regardless of the prompt. There is no actual sale or price reduction. As mentioned earlier, the substitutes carry the percentage. If this item is 10% of RP, then the substitute should get the same 10%.
I like to dig around in best practice. In the event that I get coached, I love having information readily available. They told me one time that I wasn't doing enough scanning on the weekends. Reason was because we are understaffed (I often have to work reshop while I'm scheduled instocks). My reply "Best practice states that two team members should be on instocks during the weekends in order to properly handle the work load". I also dug up a list of rain checks by departments. I can't remember the list off the top of my head, but certain departments don't factor into rain check effectiveness.