You can also break the foreach loop that outputs the extra fields into as many columns as you want. In this case, you would edit the file item.php in K2's templates and change this code:
<!-- Item extra fields -->
<div class="itemExtraFields">
<h3><?php echo JText::_('K2_ADDITIONAL_INFO'); ?></h3>
<ul>
<?php foreach ($this->item->extra_fields as $key => $extraField): ?>
<?php if($extraField->value != ''): ?>
<li class="<?php echo ($key%2) ? "odd" : "even"; ?> type<?php echo ucfirst($extraField->type); ?> group<?php echo $extraField->group; ?> alias<?php echo ucfirst($extraField->alias); ?>">
<?php if($extraField->type == 'header'): ?>
<h4 class="itemExtraFieldsHeader"><?php echo $extraField->name; ?></h4>
<?php else: ?>
<span class="itemExtraFieldsLabel"><?php echo $extraField->name; ?>:</span>
<span class="itemExtraFieldsValue"><?php echo $extraField->value; ?></span>
<?php endif; ?>
</li>
<?php endif; ?>
<?php endforeach; ?>
</ul>
<div class="clr"></div>
</div>
to this:
<!-- Item extra fields -->
<div class="itemExtraFields">
<h3><?php echo JText::_('K2_ADDITIONAL_INFO'); ?></h3>
<ul>
<?php
$efColumns = 3; /* Set how many columns to split extra fields into */
$efTotal = count($this->item->extra_fields); /* How many extra fields do we have */
$efPerColumn = ($efTotal > $efColumns) ? round($efTotal / $efColumns) : 1;
$efCounter = 1;
?>
<?php foreach ($this->item->extra_fields as $key => $extraField): ?>
<?php if($extraField->value != ''): ?>
<li class="<?php echo ($key%2) ? "odd" : "even"; ?> type<?php echo ucfirst($extraField->type); ?> group<?php echo $extraField->group; ?> alias<?php echo ucfirst($extraField->alias); ?>">
<?php if($extraField->type == 'header'): ?>
<h4 class="itemExtraFieldsHeader"><?php echo $extraField->name; ?></h4>
<?php else: ?>
<span class="itemExtraFieldsLabel"><?php echo $extraField->name; ?>:</span>
<span class="itemExtraFieldsValue"><?php echo $extraField->value; ?></span>
<?php endif; ?>
</li>
<?php if($efCounter >= $efPerColumn && $efCounter%$efPerColumn == 0): /* Reached column count so break the ul */ ?>
</ul>
<ul>
<?php endif; ?>
<?php $efCounter++; ?>
<?php endif; ?>
<?php endforeach; ?>
</ul>
<div class="clr"></div>
</div>
