Hi Wando O,
That is NOT real battery life... it is based on statistics gathering by OS itself based on your use of phone between last two battery recharge. It is not accurate especially if you charge battery for example when battery was on 50% untill 100% - best accuracy I get when my phone went down to under 10% then charge it up till 100%.
I hope this info will help you and might help others aswell. :wink: