So just a little guess 14 townies, 4 scums, that leaves 2, cause clearly we can see 20 players, but the description says--
~19 champions were summoned in the summoner rift. 14 of them in one side ready to fight and defend against a dangerous team that consist of 4 champions which goal is to rule over all of of runeterra under the command of the Grand Noxian General Swain himself. However, little did both teams know that they landed in a dangerous area where a greater evil lurks by.~
I am just guessing, the 14 townies, 4 sums, 1Grand Noxian General Swain, and the other 1 might just be a serial Killer. Just a guess. That makes 20 players as in the list, and also explains 19 summoned. As the last line says, that must be the one not counted in the 19 players.