The attached article help to understand the use of the "Ignore Background Temperature" feature in the Software Zone.
Checking this box allows the measured object’s temperature to be distinguished from that of the background. The user can determine a temperature threshold. A value outside of this temperature threshold (above or below) is considered background. Warm or cold backgrounds are definable.
If a sector/zone contains temperature values of the background, these values are ignored for the calculation of the result (on PC only).