15 R3, white spots on LCD

Several months ago, Alienware replaced the screen on my Alienware 15 R2 for white spots. Now I have another white spot which is a third of an inch high, maybe two tenths of an inch across, an inch from the bottom of the screen, nearly in center. I ran the diagnostics tests for screen, video card. Looking at the solid colors, the area stays somewhat more light than the rest of the screen in all the solid color screens. What am I doing to cause this? How many pixels need to be involved to get another replacement of screen?