www.makemkv.com

I used MakeMKV to transfer a Blu Ray. In the folder are many video files (it's a serie) and it looks, that every episode was two times copied. One time with ~6GB and one 5,9GB but same lengh.

Can someone please explain me, why this is and what is the difference?

Possibly different playlists for different regions, I see this on many releases.

For example, one playlist might be English/French/Spanish, and the second playlist would be English/Japanese.

There could be other reasons, but you haven't given us any details.

For better support, you should give the name of the disc, you could also post a comparison of one of the playlists as shown in MakeMKV, with all the details expanded.

It's Nikita The complete Series.

and the last screenshot (only can add three Attachments)

So yes, it appears to be exactly what I suggested, they have made different playlists for different regions or language selections, possibly depending on your Blu-ray player.

One set of playlists for English/French audio with one variety of subtitles.
One set of playlists for English/Japanese audio with a different variety of subtitles.

Thank you for the answer.