Can you send me a snapshot using your browser's dev tools of that portion of the code?

It looks like you have a K2 item.php override there or (worse) your K2 build is tweaked. There is no such code in K2 that renders a multi-select field's result in a <ul>. To verify, simply install the latest K2 on top of what you already have to reset and such custom styling. And of course compare your item.php inside your Joomla template's /html/com_k2/default/ folder (or another subset's) with the source item.php.