why did u shaft me

i play my promos in ranked to get placed in bronze 4 and in those 10 games i had 8 wins and 2 loses i played adc for most of them and did every well but it puts me in bronze 4... what is the reasoning behind this. i have improved greatly since last season, but i get put in the second lowest spot in the ranked divisions. my goal was to break gold but when this happens i just don't even want to play the game it is such a big let down.