G-Zip Compression appears to work but it does not

I have enabled G-Zip Compression in Hummingbird, and it appears that everything works correctly. It says that gzip has been successfully setup and all the compression options are enabled.

However, when I check the website with hummingbird, it says that there is a file that I can compress to reduce its size.

The file is locally on my server, I am not using a CDN.