Blu-Ray has 8-bit color depth and it's using signal in TV Legal (Video Range) (16-235) for bluray movies content.
Levels 0 and 255 are not used in image transmission... they used for other reasons.
So the image is 1-254, from these levels 1-16 are not used (are black) because 16 is the reference black. For the 235-254 you can have image information about these levels encoded but they are not used either in movie content.
Blu-Ray Mastering / post production studios are working the bluray content to 16-235, they have RGB Histograms, vectorscopes, out of range indicators, autolimiters, so they have real-time checking/controling for the content to be inside 16-235 range
....but during the mastering, the use RGB Space, then it's converted to YCC 4:2:0 for the bluray disk and when you playback the movie the player is converting the signal from YCC 4:2:0 -> YCC 4:2:2 or YCC 4:4:4 or RGB-Video and when it enters to your display its converted again until it re-converted at the final stage to RGB to go to the panel.
So after all these conversion, add the rounding errors, add player inaccurancies, add player problems to conversions..... maybe the 235 will go to 236 or 237 or 238.
I have a lot of reference calibration disks that have videos with 16-254 levels but these are only for testing/demonstrations, actual bluray movies they are not using 240-254 levels....
But if you like you can set your Contrast to view flashing bars up to 253 (254 is the background) but the only thing you will miss is your total peak output.... but you need a meter to set your peak output also
...A real calibration requires meter/software/knownledge, all the pattern disks are for preparing the display before using real meters, they don't calibrate your display.