Slideshow shows thumbnail sizes

Hi
I’ve got a problem similar to a resolved thread (see Slideshow thumbnail resize) but my problem is that I haven’t got 150 x 150 after the file name but it still shows at an even smaller size.
http://www.minotaurgroup.co.uk/?page_id=125
However clicking the fullscreen icon brings up the correct size and I need this to be the default.

Any ideas?

Thanks

https://wordpress.org/plugins/wp-easy-gallery/