Border Settings in Multipurpose Bookshelf Slider

Hello, i bought the plugin multipurpose bookshelf silder and adjusted the background image of the slider my wish. The problem is that you can now see in the background four edges. So top to bottom left and right you can see thin gray lines. I’ve been looking for the appropriate border settings, but not find the right ones.

Does anyone know how i can get delete that borders ?

Look at : http://www.kryoworld.com/uebersicht/

You should ask the author in comments of the file you bought.