This parameter controls the period of time to test for a 'hands off' condition (i.e. when no force is applied) before a drift (noise) calibration occurs.
IBM Trackpoints have a feature to compensate for drift by recalibrating themselves periodically. By default, if for 0.5 seconds there is no change in position, it's used as the new zero. This duration is too low. Often, the calibration happens when the trackpoint is in fact being used.