Once a subscriber list has been created, you can go back and view and/or edit the condition filters on it. Once the condition filters have been updated, the subscriber list will update and now contain only subscribers that meet the new condition(s).
On Newsletters drop-down menu:
→ Click Subscriber lists
→ Click the list you wish to view or modify
→ Click Edit subscriber list button in the top right
Your subscriber list Conditions will be displayed at the top of the page. You can remove and/or add condition filters from there.