Just a stab at this. Follow the instructions for templating at
community.getk2.org/notes/Templating_in_K2
Look for the file ...../templates/YOURJOOMLATEMPLATE/html/com_k2/templates/YOURTEMPLATENAME/category_item.php
Around line 132 see that you start to process CatItemExtraFields
Around line 137 see that you start to loop thru and display the Extra Fields
PsudoCode - Test for Extra Field Name
Reformat output of the value
Return to loop
If this info is incorrect or there is an eaiser way with css please correct me.
wjwjr