Why do you think the OS estimates a battery percentage a little above the actual value? I noticed it is always between 0% and 5% more. In particular the two percentage gets closer when the remaining battery gets lower. Maybe this way the device seems to get faster to 100%, since the 95%-100% takes a lot of time...?

Some details. I can find the percentage two ways:

* From the battery menu bar icon or with `pmset -g batt` (eg. now they say 96%)
* By calculating it manually from System Information.app or with information from `ioreg -l -n AppleSmartBattery -r` (eg. now I get: MaxCapacity: 4181, CurrentCapacity: 3813; meaning 91.2%)