We rate the capacity in Wh as it takes out the variable of voltage.
The RG1000 is rated at 39Wh, 60C discharge. This is calculated using 10,500mAh @ 3.7V.
The reason Wh is a more accurate measure of capacity is that there are many products on the market with an inflated mAh rating.
They achieve this inflated rating by using a lower voltage than actual.
We use high-discharge, Grade A lithium cells in all of our jump starters.