Yep, there is a arbitrary limit specified in the code presently but you can overcome it easily by changing the number in the file template-portfolio-4c-sorted-full-width.php at line number 19 from 50 to 100. If you want to use the shortcode, avoid all templates which start with name ‘Portfolio..’ and instead use the template – One Column No Sidebars template.
If you have loaded the child theme that comes with the theme bundle, you can just create another file with the same name as above template-portfolio-4c-sorted-full-width.php and it will replace the one in the parent theme. In the child theme file, you can customize the columns, number of items. Hope this meets your needs.