I have the same question I think. I want it to start charging at 00:30. I have no option that I've seen for 'off peak power' times. A3 E-Tron.I think I can answer the original poster's query with some confidence. With a departure time and off-peak power times set, the vehicle should start charging at the start of the off-peak power period. What I think is worrying the original poster is, if he hasn't remembered to plug in the charging cable, why he gets the alert from the we-connect app at 4:02am. I suspect this is because the Vehicle->Vehicle Settings->Notifications->Departure Times->Charging cable not connected setting in the app is set to 5 hrs. This would explain the 4am alert for the 9am departure time.
Hope this helps,