On iOS17 and watchOS10, the BatteryPhone's remaining battery power is displayed in 5% increments.
This change is due to an internal change in iOS and watchOS, and there is no way for developers to do anything about it.
Actual and displayed battery amount
Depending on the timing, this may cause the battery level displayed on the BatteryPhone to differ by 5-10% from the actual amount.
Thank you for your understanding.