How does this work?

Been working on optimizing a site for a client (I’m a noob at the prospect, so forgive ignorance). I have attached two images, the beforetest is (surprisingly) the site untouched. The aftertest is after we migrated the site to a subserver of ours and made adjustments.

My confusion is this…if you look at aftertest we managed to up the score on several different issues, but somehow we managed to go DOWN on our overall score (from 92 to 85). So what gives here? Any help, mostly so I can explain to the client, would be greatly appreciated.

Thanks
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Errm… have you tried Webpagetest?