I don't think you can reset the odometer. I found this in the Aventon Pace 500 Manual which makes me think it can only be done for a single trip:
FUNCTION 06P - ODOMETER RESET
The odometer tracks the distance you’ve ridden over the lifetime of your bicycle. Press and hold “Up Button” for 5 seconds to reset the trip distance from a single trip.
If it doesn't work then just write down the total distance you have traveled, and then subtract that from the distance you ride in the upcoming season.