Image size for graphics in hover mode

When I create a store in Market Press, it has the graphics in a hover mode, but I can't find the right size of the graphic. So when you look at the products page, like here, http://mollygreenshops.com/kittykreations/ you can see the products look blurry, unless you have your mouse right on it. How can I turn that off, so it's just the normal size? Or what size should the graphic be so it doesn't look blurry like that?