My quick maths makes this Garen dead. But he lives in game?

So firstly I'm here hoping that someone with more game knowledge than me will be able to clarify why the Garen in question lives.

_Scenario _- Garen on low health, hit by Kayle E and lives with ONE hp. (I have been suspicious of this games mathematical models for some time now, so decided to test it as this Garen was one lucky bugger).

My Quickmaths (Abbreviations used)

Garen Max HP = 2497 Garen Current HP = 118 (2379 missing health) Garen MR = 57% Kayle E = 16% missing hp as magic damage

16% of 2379 = 380 --> 57% (mr) factored = 217 damage --> Garen DIES with overkill of 99hp

_"Oh wait, what if Garen used his W" _

Garen W = 60% REDUCED damage

Factoring in the 60% damage reduction from the initial calculation leaves Garen, you guessed it, DEAD with an overkill of 12!

Conclusion

Maybe my quickmaths is flawted, or maybe there is some funny business going on. Either was I am looking for another quickmathematician to help me get to the bottom of this :)

Thanks, Trolltountilt.