The HIG can upgrade that message slightly:

title: Your session is about to end.

text below: You’ve been inactive for a while. For your security, we’ll automatically sign you out in approximately 1 minute.

action button: Stay signed in

action button: Sign out

Maybe the text could be reworded a bit. “Automatically” is redundant, everyone knows websites are automatic. “About” can do the work of “approximately”. I like how friendly they are when telling you the time limit but it may not be necessary to give a time at all. So you end up with: “For your security, we sign out sessions that have been inactive for a while.”