Q: Does the PowerPack 20000 have a smaller capacity than 20,100 mAh batteries?
A: The PowerPack 20000 actually has a nominal capacity exactly equal to 20,100 mAh. Like many 20,100 mAh battery packs on the market, the PowerPack 20000 is made of six LG 18650 (battery size) lithium-ion cells, each with a nominal capacity of 3,350 mAh. 3,350 mAh x 6 gives 20,100 mAh. For marketing reasons, the “100” was rounded off.
In short, although it's called the PowerPack 20000, the actual capacity is the same as 20,100 mAh.