Well, you are not alone, in fact, you are correct that Android Smartphones are poor in representing battery status.
Most of the Li-Ion Battery driver works between 4.2V to 3.4V and sample linearly. However, Li-Ion's discharge is non-linear (as show in the app).
This App samples battery discharge rate and give user a much better representation of the battery life.
Current Battery Status is the one shown by OS.
Actual Battery Status is adjusted for battery discharge properties.
Hopefully, with more accurate battery status, you can make better judgement in using your Android Smartphone.
Support Widget and other power saving features
此版本中的新功能：rename title bar to "Advanced Battery Status"