Dude, sometimes it takes some hours up to days until someone answers you, so keep calm.
I've noticed this too, I think the slider is for setting how the general brightness is. Mine is set to medium with auto brightness - indoors it is not too bright, and outdoors it is most the time bright enough.
"We're here for a good time, not a long time" - Colin McRae
You can't control the wind, but you can set your sails