reduced targets resistances questions

I’m wondering how “x reduced target’s resistances” works. For example, a fully leveled Manticore’s Acid Spray says “30 reduced target’s resistances”.

First off, numerically, if something had 50% resistance, it would have 50-30=20% resistance, correct? As opposed to 30% reduced target’s resistances, which would be 50*(1-0.30)=35% resistance.

Second, are CC resistances included, or just damage resistances? Would it reduce a target’s slow resistance by 30? Also, could that bring a target’s slow resistance into the negatives, and if so would that just increase the duration?

Edit: How do slows stack? If I had one source of “X% slower enemy attack for A seconds” and another of “Y% slower enemy attack for B seconds” (and X>Y) would only the X slow apply, would they stack additively, or would they stack multiplicatively?

https://docs.google.com/spreadsheets/d/1Vw7I9fTSqtx9s3a4WVvkgiOGZ7leM81n1H1RrwrOzLc/edit#gid=0
i hope this helps

oh and these only for damage type rasistances. As of i know, CC resist of enemies cant be reduced exept for freeze with 2 specific legendaries (https://gracefuldusk.appspot.com/items/8453-Shard-of-Asterkarn , https://gracefuldusk.appspot.com/items/7783-Night’s-Embrace )

The formula for category C in the spreadsheet is a bit strange, since it would actually raise a targets resistance if A + B lower it into negative.

E.g. -20 * (0.8) = -16