Actually, mAh is a silly metric to use, since Ah is based on voltage, and they rarely provide it in the spec.
Often it is based on the 3.7V cell/pouch
20,000mAh is 20Ah x 3.7V is 74Wh
78Ah would be 288Wh if at same voltage...
A 100Ah 12.8v battery is...
345,945.94594595mAh... so...