League of math, please tell me I'm crazy
Urgot With 4011 hp, and 120 armor (adjusted for Black cleaver and sudden impact, I watched the replay and that was the lowest point.) Up against an Illaoi with 371 AD and level 5 E, which if rounded up to 400 AD would do 77% of my max HP. Excluding reductions, she could have dealt a total of 3088 damage to me
Due to my reduction, assuming she didn't have any other sources of armor penetration,I looked she didn't, she should have dealt roughly 1389 after the 55% reduction. How on earth did she end up dealing 2780 damage to me? (Let's say I'm crazy, and I misremembered, let's round it down to 1700 damage. Even then, I don't understand.) I'm oh so very confused, please someone explain to me how the math applied so incorrectly. How is this coded.
Our items at the time were as follows

