If I recall correctly, it appears to be an incorrect setting in the Bios. I had the same reading. I updated the bios with the customized version floating around here, allowed the i9 to discharge to about 5 percent, and then recharged. It now shows 100% after charging.
If you don’t want to go to the trouble of updating the bios you can just live with it, as you don’t actually gain any battery capacity…