New ScanGauge weirdness

I just replaced my older ScanGauge with the new version that has XGauge. It does some weird things that I'm wondering if other Prius drivers are experiencing.

The old ScanGauge would show an MPG of 9999 at speeds of under 41 MPH when the ICE was off (e.g., gliding) and would show an MPG in the hundreds at highway speeds during warp stealth. The new ScanGauge has a "Cut Off" setting for the throttle position when the injectors would be closed and even if the ICE is spinning no fuel is consumed (14 TPS for the Prius), and the manual suggests setting it 4 higher (18 TPS). I set that, and, sure enough, during warp stealth at highway speeds I get 9999 MPG. However, at speeds under 41 MPH when the ICE is off I get an MPG in the thousands, but not 9999. And sometimes it's only in the hundreds at very slow speeds. Has anyone else seen this? Can it be corrected?

Also, I have average MPG for the current trip as a gauge. I noticed that while I was at a complete stop (ICE off), waiting for a raising bridge, that the average MPG was slowing going down! Why would this be when the ICE is off?? Anyone else seen that?

I'd appreciate any thoughts. Thanks!