I got a response from IZIP on the matter.
The range on the screen is not 100% accurate. It’s more of a snap-shot of all factors on the bike right now. This range guesstimation is extrapolated from stored energy and rate of being used, and this can easily vary greatly every second while being used.
When batteries are new, they may lose a bit of capacity right away, but be very stable over many months going forward.