Plug the car in when you hand it back at the hub; the hand back in the app asks for a photo of the cable if the car does not report it. Clause 5.3 of the rental agreement says a shared car is handed over at the state of charge in your Schedule 1, failing which the published recharge fee applies. Check your Schedule 1 under Your agreements, or check with GuyWay operations.
What charge level should the car have when I return it?
Hand the car back plugged in; your Schedule 1 sets any handover charge level.