In Simple terms that since you joined they start you @ a low level ,but as you progress on tackling the game when you drop your average indicated next to you profile (110 ).See below ;
Tiers:
When your average score is equal or smaller than 100 you go from hack to amateur.
When it is equal or smaller than 80 you go from amateur to pro.
When it is equal or smaller than 72 you go from pro to tour pro
When it is equal or smaller than 67 you go from tour pro to Master
When it is equal or smaller than 63 you go from Master to Tour master
When it is equal or smaller than 61 you go from Tour master to legend
When it is equal or smaller than 60 you go from Legend to Tour Legend*
and
you need to play at least 5 ranked rounds as hack before reaching Amateur
you need to play at least 10 ranked rounds as amateur before reaching Pro
you need to play at least 20 ranked rounds as Pro before reaching Tour pro
you need to play at least 25 ranked rounds as Tour pro before reaching Master
you need to play at least 40 ranked rounds as Master before reaching Tour Master
you need to play at least 50 ranked rounds as Tour Master before reaching Legend
You need at least 500 ranked rounds as Legend before reaching Tour Legend