Night Vision The IR brightness setting on my scope - what NV setup uses this?

[erwos]

I have a couple of Sig Whiskey5s that appear to have an IR brightness setting for the fiber optic Hellfire reticle. What is the use case for this setting? I've heard about using lasers and reflex sights with NODs, but I've never actually heard of people using scopes with IR brightness. Is it a clip-on NV/thermal thing somehow?