Someone already mentioned this but I want to clarify that mAh alone is not a full measure of capacity.

OP mentioned his mAh rating in 12 V but you’re comparing it to Ah ratings in 5 V. OP’s battery should be able to charge a full smartphone fine.

Also, most of those 10-20k battery packs won’t be able to jump start your car because they have greater capacity but cannot provide power quickly. There are high capacity battery packs that do jump start but they’re over $100 from the last time I looked.