My brother in law has a Vado 3 and has reached 10,000 miles but he can't figure out how to reset the odometer back to zero. Specialized told him to take the battery out of the display and replace it but it still reads 9999.
His bike has a TCD-W display.
I reset my TCD by holding down both buttons for 2 seconds then releasing. This resets not only the trip but also ride time, max speed, and everything else, with the exception of the total mileage (odometer). The odometer figure comes from the motor electronics. I had the motor changed on my Creo and my mileage started over. I doubt the dealer can reset the odometer, much like a car odometer can not be reset.
Not sure there's any difference between just the '-' button or both '-' & '+' buttons to reset. I just reset my trip miles from yesterday's ride by pressing '-' until the miles figure zeroed out (a few seconds). This also reset all trip-related stats; ride time, calories, max speed, etc. Only total mileage remained unchanged. Check with your LBS re resetting the total odo.