New battery lidl

Hello,
I just saw a promotion for lidl batteries.
It is 20V 4ah at 19euro. I think 4ah is too low for us.
But how many cells in serie for a nominal voltage of 20v…?!?.. I think it is inccrrect, it should be 18.8V
I will try to buy one or two… and hoping 5s1P 21700 molicel