It looks good for me in Firefox, but not Chrome. Shashin is setting a max-width on each thumbnail div, but that’s being overridden in Chrome by the overall table being pulled wider. This is a tricky one to fix in your theme. If you don’t mind showing the images cropped square, that may fix it (as Shashin uses different CSS with square images). In your shortcode, add:
and set the width to 150 or 160, and let me know if that helps.