How to show filesize when content type contains more than one file?
Actually it works fine for me without additional settings

My configuration :


I used content-type : Article and create some fields file
Your first step is good, you need to add a relationship select File Usage: File
Then in your fields section you can add : Content: Title , File: Size, File: Name




I have a listing of all the name of the file with their size.
If you want you can group by Articles.