Thanks Stennie for the reply!
I guess the mystey is solved, I was wondering where in the Atlas UI it was located 
I’m trying to achieve > meet a requirement our security team, as thy are asking if we can reduce the time out for inactive sessions to 15 mins, as the default is 30 mins.
So as long as the deployment is consistent across all replicas/shards for the timeout then it would be considered SAFE?