Everything made perfect sense on that chart when I charged it up. My 80% charger really does charge to approx 80% (55.6 V).
But what has me confused is what is happening as I approach 50V (50.4 V is supposed to be 50% charge):
I've only put 330.8 miles on since the conversion, so I have no idea if the battery is half full, or ~ 20% (one bar). The chart says 20% should be 45.4 V.