Thanks for asking this. The Monero (XMR) discount would be taken off of the total order; and it will not result in a penalty against the minimum. In your scenario, I will honor that $90 minimum because you met the $100 minimum before the XMR discount. The discount is, in fact, taken off of the total price, including shipping. So, you would save $1.50 on shipping as well. I have only had one XMR payment, and it went well. Taking the 10% from the total price just seems like the easiest way to go about it.