If you are starting with a Blu-ray movie that is only 22gb in size, then you do not need to use DVDFab for this process, other than to get rid of encryption.
This assumes you are correct about the original size!
Rip the Blu-ray to the hard drive using the Blu-ray Copy section of DVDFab, or use the free section called DVDFab HD Decrypter if your trial has expired.
You could also use another tool entirely, called MakeMKV to rip the movie in Backup mode. This will put the complete movie onto the hard drive with no encoding, so it is fairly fast. Let me know if you need any help with this free tool if you decide to use it.
Then burn the Blu-ray to your 25gb disc using Imgburn. You'll need to use UDF 2.5 file system, but ImgBurn will warn you if you have anything set wrong, so follow its instructions.
This whole process should take about an hour, maybe a bit more, to rip to the hard drive, then burn the disc.