Anyone else bothered that they do not specify the energy in watt-hour? Back when USB was 5V it was pretty easy to do the conversion from Ah, how does it work now that USB can negotiate voltage dynamically?
You should be able to calculate the watt hours based on the voltage of the internal batteries. Its likely a 3.7v lithium, so this anker bank would be 3.7v x 24,000mAh = 88.8Wh
The issue is comparable to mileage numbers... I dont trust that at all.
Usually they just multiply the number of cells with their "rated" mAh-value, but who knows what their cutoff voltage is. Also you need to integrate over the voltage (which keeps falling during discharge) and the discharge graph also depends on how much power you draw. Then the 4.2V=>5V (or 9..19V for USB PD) conversion losses are also not counted.
Anker does specify the Wh ratings. Just on the battery itself, not the website. In flyspeck 2.8pt size font (I just checked with my Peak 10x inspection loupe with reticule, the characters are exactly 1mm x-height), dark gray on black for maximum unreadability, that needs a microscope to read. On my 737, it says 86.4 Wh.