Well that is the beauty of it, you can take a compressed format, and compress it even more to save space/storage, send it via email etc. I don’t know of any other software that can compress already heavily compressed files to such an extent.
No matter the file, the compression ratio will always be 50-60%. The way the algorithm works it’s file format independent (yes, very out of the box compression, I know).
The files will be in an archive.