How does facebook choose what mutual friend appears in the parenthesis when I get a friend request?

[basketball14]

Whenever I get a notification on my phone from facebook, saying that someone wants to be friends, it always shows the same person in the parenthesis behind it.
ex: so-in-so wants to be friends on facebook (friends with so-in-so) ??

[Live from my sofa]

Not entirely sure, but I beleive it chooses at random from the list of mutual friends, but any that you interact with a lot will be more likely chosen that someon you don't interact with.