Why is the contrast ratio lower than the claimed value following the result of a measurement?
This is a normal phenomenon for monitors calibrated at the factory. Contrast ratio is luminance of the brightest colour (white) to that of the darkest colour (black). Due to factory calibration procedure, a panel's white point needs to be adjusted to standard 6500K and thus reduces the maximum brightness of the particular unit. As a result, the contrast ratio becomes lower than claimed.