Match grade issue :/
Hello people! So yesterday i played a match as katarina,i had 13/2/2,61 cs and the enemy team surrendered at 17:30. I got S+ for that. Today i had 13/2/2 again,100 cs and the enemy team surrendered at 22:40.I got A for that (proof for both matched is on the screenshot i uploaded ,clicck the link to check it). Why did i get a lower (way lower) grade even though i had 39 more cs? can someone explain to me what the match grade depends on? Thanks in advance!!! :D [katarina-love]