How is card progress calculated?
Epic status automatically turns to Done, when its checklist and subcards are 100% complete.
When some checklist items or subcards are not complete, you see the progress bar, filled in so far as how complete the task is.
In case of ordinary cards without subcards, the progress is entirely based on checklist.
If a card has neither checklist nor subcards, card status can be added manually by checking the box Done on a card.