Highlight/Shadow protection

I would like to know exactly what does the highlights/shadows protection faders located under many filters inside Color Efex or under Global settings in Silver Efex.
I understand, it should as it say protect (so don’t touch… = leave as it is) the shadow or highlights
BUT from my experience, many time, it really doesn’'t look that way… even, it look the oposite way…

So can anyone explain this ?