WebPlus X6: Slide Thumbs

I have this on my web page http://serifaddons.com/slide-thumbs-demo.html

But for me the 4 thumbs are not centred under the main picture, they are slightly to the right and I need to fix it as I would prefer them to be centred. I have tried editing the code but I can't see which part needs to be changed.

Please can anyone advise?

Thanks