We’d like to advise that there is always a conversion loss when the power is sent from a powerbank to the device being charged and this is normal for every charger.
If you’re unsure, here is how to calculate what charge % the Flash Powerbank can achieve for a specific device.
Let's use an 87W MacBook Pro 15" as an example. The best way to answer your question is using the following formula which calculates the conversion of watt hrs to mah whr = mah/ V*1000*70% (output efficiency at 20V) .
The Flash is 74whr/3.7v x 1000 * 70% (efficiency at 20V) = 14000mA.
The Macbook Pro 15" = 83.6 whr = 22,000mah = 63%.
The Macbook Pro 16" = 99.8 whr = = 26,972 mah = 52%
In another example with a 29.37Wh Ipad Pro 11, 1.75 times is about right as that's 51.3975wh 74wh (flash) x 70% (remaining power at 20V after conversion loss) = 51.8wh.
In order to use the above formula, you firstly need to convert Whr to mAh correctly based on volts. The volts of the battery inside Flash is 3.7 volts. Using the example of a Macbook Pro 16" again
To calculate the mAh of your particular device, please vist this site.