Hi MuffinMan!
The folder links are only there to use if you want to import the files to your own mega.nz account. They are way too big to be of much use for straight downloading.
As far as an ROTJ 25GB disc, there isn’t one.
NJVC’s ISO’s require the follwing sized discs:
SW - 50 GB Dual Layer Blu-ray
ESB - 50 GB Dual Layer Blu-ray
ROTJ - 50 GB Dual Layer Blu-ray
SW Documentaries - 25 GB Blu-ray
ESB Documentaries - 25 GB Blu-ray
ROTJ Documentaries - 50 GB Dual Layer Blu-ray
The ROTJ Extras Disc has so much stuff on it that it needs a 50 GB Disc just like the main feature.
As far as what links you need, if you are looking to download the ROTJ Documentaries, scroll down to where it says:
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Return of The Jedi BD 50 Docs Links
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Under that it will say "Folder Link:"
Under that there will be a single weblink which you can ignore for the reason I mentioned above.
Under that it will say "File Links for FreeRapid Downloader:"
And under that there will be a long list of mega links.
^Those will be the links you need to download if you are using my guide to get the NJVC ROTJ Documentaries ISO.
They are all pieces of the ISO file, split into smaller chunks so you can download a really huge ISO file in smaller parts instead of all at once.