Battery capacity generally refers to battery nominal capacity.
It is the approximate capacity the battery can release out when constantly discharged at 0.2C rate（C rate=Ah/h）to cut-off voltage at 20± 5°C. Usually abbreviator C stands for battery capacity and 0.5C refers to the half of battery capacity in battery field.
Capacity unit is Ah or mAh, calculated by multiplying the discharging current (in Amps) by the discharging time (in hours) and decrease with increasing C-rate.
Generally the discharged capacity is related to temperature, discharging current, discharging time, cut-off voltage, internal resistance and charging voltage.
In domestic market, some battery manufacturers will falsely mark higher capacity than real capacity. In normal use, it is difficult for final users to know if the manufacturers falsely mark or not. It is also hard to do test due to lack of equipments. The price of equipments in the market is at the level of $3,000 which is not realistic for normal users to own one.