The setting you've referred to is the differential and not the temperature bias that @JasonJoel and I referred to . The differential determines the minimum temperature change required for an auto-switchover from heat to cool and vice-versa.
The temperature bias (or offset) is ISU #1420 (in the manual you linked to). It's purpose is to correct between the actual temperature (eg. obtained as an average of several sensors) and the displayed temperature. This is restricted from -3F to 3F, which is very small compared to most thermostats. For example, the Vivint CT200 has a bias of 6 degrees (-6F to 6F), and I believe the GoControl has a bias of 10F.
