I think the point is that staring at a sun-bright computer screen is supposed to mess about with your circadian rhythm as its effected by cues such as light levels (bright light = daytime, low light = night time). Staring at such bright screens for prolonged periods can supposedly confuse your body re: time of day/appropriate sleep responses. So in theory, this should try to mitigate some of those problems, at least in part. No idea how effective it will be, but I'm going to give it a try as I know I have trouble sleeping soon after using a computer.
That said, it's not going to decide for you when it's time to go to bed, that's up to you!