Unfound Loot

My bad, I forgot how it works myself. For modifiers higher than 1.0 there is a different formula:
(1 - Math.pow(1 - 0.85, 1.1)) * 100 = 87.59203999415325
where 0.85 is the global chance, and 1.1 is a modifier

You can test different values in the browser console (F12 -> Console)
(1 - Math.pow(1 - 0.90, 1.5)) * 100 = 96.83772233983163
(1 - Math.pow(1 - 0.50, 1.2)) * 100 = 56.472471835193794

The point is, the removal chance stays below 100% to compare it with the dice.