A funny thing happened on the way to the….  Actually, the funny thing that happened was I was trying to embed a Google Presentation into a Google Site that was not on the same account.

I had the presentation open in Google Chrome.
I had the Google Site open in Firefox.

I copied the URL of the presentation in Google Chrome.
In the Google Site I went to the insert menu and I wanted to insert a presentation.
Instead of choosing a presentation from the list I pasted the URL of the presentation at the bottom of the insert screen.

I noticed the url had #slide=id.p9 at the end of it.

When I hit save it had the presentation embedded but it was showing  the 4th slide in the presentation. (If you rearrange the slides the numbering gets mixed up).

I attempted to replicate this in WordPress but it only seems to work in the Google Site. So if you are embedding into a Google Site, you might be able to copy and paste the URL from the presentation from the page you want to start on. You will need to copy and paste that URL at the bottom instead of just choosing the presentation from the list, but it just might work.