The float will fill until it is near the top of the post and start filling when it is near the bottom, trying to set an exact water level is not easy and will change a couple mm as the float breaks in, I would not really get overly concerned with that, but as a general rule about 2mm from the c clip is start and 2mm from the nut is off, this gap tightens a bit as the switch wears so the level fluctuates less. The jumper on 1 pin is 3 minutes (25-55 gallons), the factory setting on 2 pins is 1 min 48 seconds (5-25 gallons).