Ok, well this was stupid of me.
The arrow icons to the side of the menu cards are navigation arrows. I just remember from looking at the demo that there seemed to be more than two items so got confused.
Anyway, if anyone else is wondering, menucard.php contains two lines which state
`$catsperpage = 2;
if ($onecolumn) $catsperpage = 1;`
Amending the numbers here will add extra categories to your menu cards. The first line is for the two column layout, the second is for single column layout.
Be aware though, that if you have not created a child theme, do this now. If you dont, whenever an update for this theme comes out, that file will revert back to the original settings and your changes will be lost.
Information about Child Themes can be found in the WordPress Codex.
I hope this helps.