Still Trying To Understand iCloud Process

I recently opened a downloaded zip file of music files.

I then dropped the folder into Automatically Add to Music folder. I noticed my iCloud folder in the sidebar processing an upload, but at a size not comporting with the size of the data dropped into Apple Music.

I tried to search my iCloud folder, but I assume this iCloud upload process was really or basically uploading to a non specific Music matching protocol, or something.

Any thoughts on why a 100mb data size differential would be observed in this process. The original data size is 300mb, but the iCloud process calculates it as 200mb

not to mention, when navigating back to the iCloud process icon, it change the upload from one item at 200 mb to 2 items at 200mb

Completely non-intuitive to me