How does Cubase backup reduce file size?

I just backed up twelve short audio tracks (choral music). After Backup, the original file went from 298 MB to 165 MB.
Before I backed up, I had already emptied the trash and removed .BAK files.
So can anyone tell me exactly what was removed to gain this reduction in file size? Were the .wav files compressed?

It probably got rid of unused audio files, and edit files.

Of course, wav files are not compressed.

OK, thanks. But I’d already removed the files not used in the project and emptied the pool trash.
It seems like a big reduction. What are edit files?

See Audio Files and Audio Clips

Thanks, then.
Have a good evening.

You’re welcome! It’s still morning here :sunflower: