How to add unsubscribers from a list to a segment

Hello there, 
we want to know a bit more about our unsubscribers. 
Especially where they are located. 
So my solution was to do a segment where all unsusbscribers will be added as soon as they unsubscribe from a certain list. 
How do I create this segment? 
There is a way to say 
What someone has done or not done….
Unsuscribed from a list…

But there is no filter to specify what list. 


Would be great to get some ideas. May be there is an even easier way?

Best regards

Tobias