Topic: SimpleViewer not showing larger image

I need to know how to chage the way SV show my image in the preview window.  You can click on "see larger image" and the image is there.  My image sizes are 600 X 450 but in the preview screen, they show slightly larger than thumbnail below.  I am using it on a wordpress blog.  HELP please.

the site is in development and is
www sellfortsmith com and click on the 1904 Eastgate post to see SimpleViewer.