Does each bar under Gear Battery really represent 20%?

The Gear Battery bar display (which I hate) appears with five bars.  Logically, one would think each represents 20% of the total battery.  I am using this on a 12-speed di2.  Typically I can get two six-hour rides using one "bar" or with 20% of the battery.  However, today I started a ride showing 3 bars and so 60% of the battery available (perhaps 50% depending on when the bar drops).  Early in the ride it dropped from 3 bars to 2 bars---now in red with a warning message about "low" battery.  This has happened before but at the end of a ride.  I assumed that I had at the very least 40% left.  However, four hours later it dropped from 2 bars to 1 bar with another warning message about "critical" battery.  This would not make sense unless these bars are not all 20%.  Does anyone know for sure?  My guess is that 2 bars actually means 25% and that 1 bar means 15 or maybe 10%.  This would be in alignment with those warning messages I get with the Garmin Radar.