Just Got Two Chests and Two Key Fragments Playing Support

Please read my post before Downvoting... A lot of people are downvoting because they don't know anything about Hextech Crafting, my post is not about earning Chests and Keys, it is about me asking how and why I earned S score.

First game I was Zilean, went 10/10/24 out of 52 kills. Also did the most damage to champions in the game. Didn't build a Sightstone, but still placed the second most wards in the game. It was a 47:23 game.
http://matchhistory.na.leagueoflegends.com/en/#match-details/NA1/2126452109/206176227?tab=overview

Second game I was Blitzcrank, went 7/5/19 out of 44 kills. Did more damage than most of their team, except for Quinn and Azir. Placed the most wards and earned more Gold than our ADC and all their team except Quinn. It was a 29:21 game.
http://matchhistory.na.leagueoflegends.com/en/#match-details/NA1/2126456931/206176227?tab=overview

I don't ever play either of those champions, so I am not sure if that had something to do with it, but I personally don't think those are S performances. I have gone way more positive with Janna or Nami and got A's instead. I really would like to know how I earned this S, what did I do exactly?

Please check this out and upvote so Riot can see: http://boards.na.leagueoflegends.com/en/c/skin-champion-concepts/juvJ5Trc-match-history-should-give-you-in-depth-champion-mastery-details

EDIT: Seem like I am being Downvoted because people don't believe me or are misunderstanding what I am saying.

http://imgur.com/zC7ozqU http://imgur.com/2HC6lcd http://imgur.com/XsDB08X

You can see here I have opened my first day Chest and got Lolipoppy, Battlecast Ward, and Essence. Then you can see 2 chests and 2 Key Fragments. In the next two pictures you see I that I got an S with Blitz and Zilean and that the Chest symbol is filled in and they have a unique border.

EDIT 2: I'm not sure where people are getting this "one chest per X days" thing, from what I read you get 4 chests a month playing, you can only earn 1 chest with each champion a Season. Meaning you need to play a different 4 champions every month to get a chest for the rest of the season.