Teemo shroom dmg bug

so it says :" It detonates if an enemy steps on it, dealing 200 / 325 / 450 (+50% of ability power) magic damage by poisoning nearby enemies..." then how a teemo with 310 ap luden + sorc boots can do 800+ dmg vs my 94 magresist? Cause this happened. Is that a new hack or buggy game or just typical hidden buff from riot?

Calc in comment the game is clearly buggy!!!!