This post illustrates and explains the 4 jumper settings.
The jumper selects the desired temperature offset.
Really hot, use the -10°C offset setting.
Really cold, use the -30°C offset setting.
Rest of the time, use the factory setting of -20°C offset.
Note: The -0°C setting turns off the IICE Air, and operates from the stock sensor.
Jumper settings, monochrome all-in-one:
Jumper settings, color detailed: