In USA, I always see portable batteries for mobile phone stating they have 5000 mAh, 10000 mAh, or 13000 mAh, etc. (One of the popular one is Anker as on Amazon.com). However, in Asia, I saw the batteries having a spec of 10000 mAh "battery capacity", but a "nameplate capacity" of 6200 mAh. Another battery was 10000 mAh but its "nameplate capacity" was 5100 mAh.
The word for "nameplate capacity" is "額定容量" and it seemed to mean "effective capacity". It seemed 10000 mAh is relative to 3.6V of the internal batteries in the charger, and the effective capacity is relative to 5V. (and if it is for QC 2.0 or 3.0 and 9V charging, then the mAh drops to close to about half).
How can we understand this? Does that mean batteries like Anker stating 10000 mAh is also nominal and it really has an effective capacity that is not stated?