The Placement Matches Assessment Bugged?

I just finished my placements and won 8 out of 10. I was really pumped about that. OH! WOW...I'M SENPAI, NOW! But after the score got processed, I achieved Silver 4 rank. WHY YOU NO GIVE ME HUG? YOU SLAP FACE. WHY??? Last season I ended in either Silver 3 or 4. I don't know if it's a bug but is that right? Does this make sense? I mean, I tried my pingers off. I won 8 out of 10...C'MON! That is equivalent to a B on a test, an 80% on an exam and a 3.0 GPA on a report card. So what am I missing here? I just got a great score on a test and I get punished for it by being placed down from last season or staying the same rank? Riot, I understand there are bugs everywhere in League and not everything is perfect...BUT there is no excuse for this. Is there something that I need to do or focus on when playing in order to rank up in the fashion I deserve? How does the Rank system work so I know what is absolutely necessary for me to achieve the greatness of Master and Challenger? I just want to get what I have worked hard for and escape the clutches of Silver. I need to see something for my honest hard work. I play League almost every day and I enjoy it. Even when I get angry, I come to league to have a good time. Please, Riot, for a regular player. Don't break the camel's back, not now not ever. Be fair. Be the company that gives just treatment to its customer. I want to continue playing but after this stunt...I don't know if I can find it in my heart to re-install.