is this an a- worthy score?

i go 8/2/26 as ziggs in aram, deal second most damage aside from enemy garen, win, and i get a a-. my cs is is awful, but its aram, my kda is good (17) so what do i have to do more of to get an a-? meanwhile i get irelia in aram, go 15/7/19, deal 20k damage compared to the 40k kennen, and get an s-?

https://media.discordapp.net/attachments/493044365560905736/499373076543307807/Screen_Shot_2018-10-09_at_8.06.06_PM.png?width=400&height=101

https://media.discordapp.net/attachments/493044365560905736/499373137302126602/Screen_Shot_2018-10-09_at_8.10.23_PM.png?width=400&height=80