Category Issue

Hi, I am using the plugin to display thumbnails of posts on all several of my site’s pages and instead of just showing the category specified it shows all categories. For example, http://www.ajoyfulriot.com/home-decor-diy/ shows all posts despite category and the shortcode I am using is this: [thumbnailgrid posts_per_page=”999″ cat=’6′ order=’DESC’]

Thanks so much in advance!

https://wordpress.org/plugins/thumbnail-grid/