I created a special coupon for one of my patrons (that I was planning to use as a model to create for others) that was $25 off my shop, applicable to certain products.  Instead of coming off the total of those products, it took $25 off each product in that category, for a total of $50 off. 

Something similar had happened a while back when I had a coupon for reduced shipping costs for a singular item - which ended up clearing out the shipping cost completely if someone ended up ordering multiples of that item - that was definitely unplanned.  That wasn't a big deal since it was $4, but multiples of $25 definitely not cool. 

Is there any way to get a dollar amount that's specific to a category, but doesn't repeat itself in the same order? It was set up to be just a one-time coupon.  Ideally I'd like to limit which items get discounted AND make sure the coupon only applies once per sale.