Content Width tiled gallery

Hi I have a problem with the width of the tiled gallery. It is adding 5px to the right edge even though my content width is correct at 960px? I’m a perfectionist so wold ideally like it to be inline with the navigation. Is there a way of changing it within the plugin or my functions php? Its perfect on the square gallery?

http://brightmist.co.uk/simplicity/

Any Ideas?

Thanks
Judi

http://wordpress.org/extend/plugins/slimjetpack/