Maximum capacity description
According to the space of the power bank.(130*75*17mm).
The largest capacity of the atteryis 8000 mAh.
All of this shape which capacity more than 8000mAh are fake.

How to Calculate the working capacity:
Battery Volatge(Input Voltage): 3.7V
Power bank Voltage(Output volatge): 5V
When working, it may lose 15-25% energy
Working Capacity=8000mah3.7V/5V75%= 4440mah