Migration LrC to LrD: Folder question

Dears,
looking at attached screenshot from LRCC, I created in Classic 2 "test catalogues", marked in YELLOW- just for trial how migration will work.
In this way I created collections in Classic to reflect my folder hierarchy and to have it similar in Desktop.
So far, it fulfills my expectation but one thing is astonishing and maybe has a simple reason:
2 more folders are created in CC with the same naming as the catatlogues, including all photos w/o hierarchy (marked in RED).
First assumption was this could be the original versions, but they weren't.
Can anyone explain this "feature" and what 's the background of it?
Can I simply delete these additional folders w/o loosing important information?
Thanks upfront for some advise.