Why two copies of movie on UHD disk

[DonPM]

Probably a naïve question, but when I rip the Bladerunner UHD, I see two ~50 GB mkv files. Each is a complete copy of the movie (identical, not different cuts of the film), but different file sizes. What is the difference between them? I don't want to save both on my hard drive.

[Deano86]

Theorized here.....

http://makemkv.com/forum2/viewtopic.php?f=12&t=16967

[DonPM]

Thanks! (and oops, I posted my question in the wrong sub forum)