How does Elemetal Mastery Exposure Works?

The pasive says

"

Exposure you inflict applies at least -18% to the affected Resistance

And I wonder how it will works in case the caster can actually reach higher exposures, but not by the main skill wich gives that exposure.

For example: Wave of Conviction gives -10% fire res, Fire mastery gives -5% fire res, and elementalis gives another -25% for a total of -40%

It will be at least -18%, then -5% and -25% for a total of -48% or it will just not work because I have more that -18% in total?

Ty in advance for the help :D

"

Arathatron wrote:

It will be at least -18%, then -5% and -25% for a total of -48%

This one.

upd. Based on the wording of Elementalist's ailment notables I believed it would work like that, but in the game it actually doesn't.

"

It will be at least -18%, then -5% and -25% for a total of -48% or it will just not work because I have more that -18% in total?

Yes, so the mastery bonus is discarded when your final exposure is stronger than -18%.

This makes sense and this is how it's read initially, without having in mind Elementalist's "at least" from "Shaper of ..." notables.