Data Text box not full width

Hi, I’m running a custom theme and the datatext box beneath each lightbox image is about 10px shy on each side of the image. Almost like the border for the data text is missing. As near as I can identify the offending div is lightbox-container-image-data-box.
Any Ideas ?

Production site here http://crowds.slashdash.co.uk/gallery/

Jim

https://ww.wp.xz.cn/plugins/simple-photo-gallery/