yeah, zero chance that's 20 ah.
I'll never stop saying it, never trust cheap cells. Burn your house down. Likely that pack is more like 8 or 9 ah, and 6 or 7 ah in actual usable capacity. It will sag like grannies tits. Its a hoverboard battery basically.
But 4 of them in paralell, that's a possibility. Just keep em outside!!!
Lastly, your money will travel to china easy. The battery not so easy at this moment. So don't send your last hundred bucks, send the money you would have spent in a bar.