Histogram strangeness

[Matt Snell-Callanen]

Here's a screenshot of a histogram before & after an exposure adjustment.  (this is a still frame from a UHD bluray movie in Photoshop)

Can anyone tell me what the vertical "lines" might be indicating? My only adjustment to the image was bringing the Hightlight side down so the highlights in image are closer to RGB 255 in 8-bit. 

To my eyeball.. the image looks fine after adjustment. I just wonder if there's some degradation happening from the histogram's strange appearance. 

 

[Perry Paolantonio]

the vertical lines are usually there because the image is 8 bit or less

Edited December 2 by Perry Paolantonio