Question with Scorch (reduced resistance) when enemies have negative resist

Like the title, I was wondering if like reduced elemental from The Annihilating Light staff, scorch reduced minus resistance of boss monster so it mean we do less damage to them or my understanding is wrong somewhere ?

The Annihilating Light affects YOUR resistances only. Also you can apply Scorch to a monster that already has negative resistances.

OP: Annihilating Light minus res is a drawback to your character. It is NOT a buff to your damage.

What I mean to ask like for example:
I make sirus have -20% lightning res.
When I apply scorch with Legacy of Fury boot, it reduced elemental resist for maximum of 30%, so does it mean reduced -20% for like maybe to -16% which reduced my damage.
It is correct ?

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LelouCG wrote:

What I mean to ask like for example:
I make sirus have -20% lightning res.
When I apply scorch with Legacy of Fury boot, it reduced elemental resist for maximum of 30%, so does it mean reduced -20% for like maybe to -16% which reduced my damage.
It is correct ?

What would make your ever think that?

First of all Sirus starts at 50% resists, to put him in the negatives would require much more than -30%.

If you reduced his resist by 20 and then by 10, it literally means reducing his resistance by 30.
It does not matter what his base resist is or if it is negative already or if is non existant.

-20 and then -10 is always -30, there is no interaction and nothing else going on.

In this example you would reduce his resists from 50% (his base resist) to 20%.
If you would reduce it again by 30%, he would be at -10%, and so on...

The same is true for penetration, it just ignores at certain % of resists.
Even if he is already in the negatives.