you reset the timers/counters etc by holding down both buttons for a few seconds.
Also, learn to zero the torque:
Use the Mode button to get you to the Watts reading, then while viewing instananeous wattage, hold down the select button until the "watts" lcd flashes. This is hub torque. Now get off the bike entirely, or just coast, but make sure there is no torque on the hub, then hold down the select button again until the torque reads zero. Once this happens, hit the mode button once to get back to the watts display.
All of this is in the manual, available from the saris website in pdf.