Game dmg calculation is buggy!!!!!

Teemo 1 shroom dmg calculation vs real dmg it did: stepped on one shroom with max hp

so here are the stats + calc: My stats: max hp :2164 mr:91

teemo: items: sorcboots,liandry, luden, void ap: 296 shroomlvl3 runes: mistic comet

Dmg it actually did aprox: from max hp down to 1287 = 877dmg

Dmg it should have done aprox: teemo: 296ap shroom dmg: 450+148 =598 luden dmg: 130 liandi burn dmg (7.5% maxhp) : 162 misticcomet: 155 all dmg is magic :598+130+162+155=1045 liandry bonus ~4% ->1086

Mr dmg reduction: mr:91 mr pen 18+40% mr real: (91-18)0,6 = 43,8 dmg multiplier: 100/143,8=0,695 all dmg should be: 10860,695 = 755

755!=877 shroom + items did ~16% more dmg than they should have clearly the game dmg is buggy!!!!!!!

feel free to blabla about how this calc is wrong oh and dont forget to post the fixed one , until then the game is buggy