1. What is his one-rep max?
2. Write down a guess.
3. What information would be useful to figure this out?
4. Write down some questions you have in your head right now.
5. How does the website calculate a one-rep max? What formula could describe it?
Update: Jeremiah found a great solution with Desmos:
Using a Desmos regression, it looks like the relationship is either cubic or quintic. https://www.desmos.com/calculator/dep61qtq48