Print out this section on paper:
Now write the name of each folder (not any file names, as the split level strictly deals with folders/directories) on the paper. There is not such thing as a 'sub-dir"! It is either a folder or a file. I do believe at this point, you need a split level of at least three. (By the way, I doubt if you truly need any split level if you are using .mkv files for media storage. Each show or movie is in one (and only one) file and that means that there will be no pause in the playing of any movie or show while a second disk spins up. You may have a slight delay while loading file names but that is usually only a few seconds.)