Won 7/10 with amazing KDA and got placed in bronze V. Bug?

Hello fellow LOL players.

Today i decided to play on my EUW account which is a few years since i've last played on. I played my 10 placement games and won 7 out of 10 games, with me carrying all of them and having a very very good KDA.

I got placed in Bronze V, the absolute worst division there is in LOL. How is that even possible with 7 wins, not even taking account for my KDA and carry. This is by far the best placement matches i've ever played so i was very shocked by this result. I have played far worse placement matches on totally new and fresh accounts and got silver 3?

This must be some kind of mistake since there is no logic, mathematics or rationalitty behind this placement, and i can prove that with my latest game in this division called Bronze 5. I am now not only ruining the fun for myself by playing against beginners, i am also ruining the fun for a lot of other people trying to climb Bronze.

Proof Link: http://imgur.com/a/dEAgC

I have decided to submit a ticket to Riot because this is too absurd. What is your guys perspective on this, it must be a mistake or some kind of misunderstanding right?

Here is link to my ticket and what i wrote to Riot Support: http://imgur.com/a/ORZcs