How to get optional discount applied only to rent on a quote

BlueMtnCabins asked the same question in this article: https://www.ownerreservations.com/blog/enhanced-surcharges-discounts-and-add-ons
And it looks like it was resolved at the time. But when I added an optional discount for repeat guests and tested it, the discount appears below the cleaning line, so it's taking the discount off of the total, not just the rent line item. How can I get the discount to apply only to the rent line item?

Percentage items apply to items above them, so you need to make sure the discounts are at the top. To do that either:

a) give the discounts position and give the surcharges a blank position (which will make them come after discounts)
b) give the discounts a lower position like 5 and the surcharges a higher position like 10 -- they're ordered in numeric order