What determines the order of posts in "Up Next" using the Magazine template?

Up next are posts adjacent to the current post in the list of posts. Latest posts are the most recently published posts. Please let me know if you have any questions about this or anything else

I was seeing odd behavior in the Up Next and Latest Posts when I had a home.md in the root of my site. I will put it back and see if it still happens - if I does I'll drop you a note. Thank you for taking the time to answer!