Hello Simon,
This is the default functionality, one column per user/category. If you wish to change this you have to manually set 50% widths and floats. the files you need to edit are located at templates/yourtemplate/html/com_k2/default ( or what override your template is using )/ latest.php and latest_item.php.
I am sure the template developer can provide you with valuable info on the template and its structure.
JoomlaWorks Support Team
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