S+ question

So, what is the criteria to get an S+??

I've played this game

http://matchhistory.eune.leagueoflegends.com/en/#match-details/EUN1/1490127026/204624139

my farm is ok..not the best..the game was 4 vs 5..and i actually carried lucian KS'ed me..and he got more fed than me..but neither of us got S+..we got S