13/0/13 Yasuo and I got A+

the system isn't all that accurate.

it goes by what the average player gets, yaso so broken average player usually goes 20/0/20

Only 190 CS in 30 minutes. You might not have helped with enough objectives for S rank either, can't say without seeing more.

Because of your CS. I think that it compares you to all yasuo, so you probably needed about 250+ CS to get an S

That CS at 30 minutes is not acceptable for S.

I also assume that you didn't ward much or participate in objectives but I can't say without seeing.

CS, as others have brought up, is very heavily weighted in your score. You need to aim for about 100 cs per 10 minutes (you'll fail at this, but it's ideal), have good kill and objective participation, take towers, ward, gank if possible, and have a low death count.

KDA is by no means the end all be all of the mastery score.

Your CS is too low for the game length. You should have been well over 200.

CS to low for a yas even though you had the most farm on yas they are looking for at least 250 around 30 min and wards placed im guessing you placed wards since norm you dont get A+ unless you almost had S so yeah thats at least based on what others have told me

CS better

LMFAO, Rito no like you