Can you tell me why 'Optimize PDF...' isn't optimizing type on a page? (pics included)

[Overground555]

I'm trying to optimize a book that is several hundred pages long so it's (hopefully) easier to navigate in Acrobat, but no matter how low I crank the downsampling to, it isn't changing the copy a single bit. How do I change the type in this book so that it's a smaller file size, and will allow me to scroll through acrobat with less lag? The file still comes up to be over 20MB in size.

A page that's been heavily compressed

A page that hasn't been compressed even a tiny bit

Settings I used just to test the compression

[Bernd Alheit]

Click on "Audit space usage..."

What does you get?

[JR Boulay]

Try to untick this checkbox: