It’s on the “What You Need to Reach Medallion Status” page.
Scroll down to the “Things to Know About MQMs” section
and it’s in the third column, “Bonus MQMs”

“When you book a higher fare class, you’ll be rewarded with even more MQMs. Full fare First and Business Class tickets (F, J fares) are eligible for a 100% MQM bonus. Discounted First, Delta Premium Select, Business, and Premium Main Cabin tickets (P, A, G, C, D, I, Z, Y, and B fares) are eligible for a 50% MQM bonus. Purchased upgrades are eligible for bonus MQMs based on the class of service flown.”