How to slow down the slide show for the Gallery theme

How can I control the speed of the slideshow. I have text included with the images and it goes by way to fast.
I saw a previous post that Tammie commented on but didn't really understand what she was saying, but the gist of it seemed to be "no" you couldn't control it.
I remember that I had a similar problem with the Studio Theme, but I think an updated version was the solution there.
Is it possible to edit the slideshow function to include this parameter, as seen below?