I had the same issue with my (my hub did have another issue too that I returned for a refund [control knob was working intermittently). But iFixit support provided the following. "The battery, being new, is still in the process of calibration. You can follow the battery health reset guide, but over time that percentage will likely go up, as the battery learns more about the charge-discharge behavior." Reset Guide FixHub ウェブコンソールの使い方 As part of the troubleshooting of the other issue that my had I had to disassemble the hub (FixHub ポータブルパワーステーション UIボードの交換) and when the battery was reconnected the battery health read as 100% again. Hope this helps :)