What does it take to get an S as a Jungler?

I recently played Kha'zix Jungle and had a great game, but did not get an S.The game lasted 22 mins long(they did not ff). -I was 7-1-3 with 118 cs -placed 6 wars and killed 1 ward -i was level 13(the highest level in the game)

My Top laner Got an S, but he was 4-2-4 with 143 cs, and placed 8 wards and he was also level 13.

What was the reason he got an s and i did not?