Hi Jim.
The In-Run Bias Stability specification represents the bias accuracy you can achieve under stable inertial and environmental conditions. This specification is derived from the minimum point on the Allan Variance curve (located in the Typical Performance Curves section in the datasheet). In effect, this behavior establishes the best bias accuracy you can achieve, after calibration. What type of specifications are you used to reviewing? Can you post a link to an example?
Thanks,
NevadaMark