That specific number next to the folder name is letting you know how many “items” you have in that specific folder - the number itself isn’t tied to a specific “stage”, “status” or “priority” of your items.
What I can suggest doing is, whenever you are done with the task / project that has “closed” status, you can move it from that folder into an “archive” / “completed” folder. Once the item is moved to another folder or removed completely - the number next to the folder name will decrease (it will be deducted by the number of items you moved / deleted) and in that sense you can track if you still have tasks to work on or not.
Moving items when a certain condition is met can now be done easily with our automations.
(you can use trigger “attribute value changes”, condition - where status is “closed”, action “move item”)
Let me know if that helps @michel