Smush Pro not smushing enough according to Google

Hi,

We're desperately trying to reduce image size on our site, we're resized them using plugins, used the Smush Pro (super-smush, smush original image, do not save image backup) and still are getting these results: http://prntscr.com/a23zeo most of them being able to reduce it's size to up to 87%

What else can we do?

thanks!