I believe sub-columns are what you're looking for. From the Zurb documentation:
While the Ink grid can't be nested like its Foundation counterpart, Ink does provide a nestable sub-grid for when one grid just isn't enough. By applying a .sub-columns class (as well as a numbered class, same as the primary grid) to a tag underneath a .columns table, you can sub-divide the .columns table into sub-columns.
Markup
<table class="container">
<tr>
<td>
<table class="row">
<tr>
<td class="wrapper">
<table class="twelve columns">
<tr>
<td class="four sub-columns">
<table class="button">
<tr>
<td> <a href="#">Assigned</a>
</td>
</tr>
</table>
</td>
<td class="eight sub-columns last">2/12/2013 12:14:00 Reboot Server</td>
<td class="expander"></td>
</tr>
<tr>
<td class="four sub-columns">
<table class="button">
<tr>
<td> <a href="#">Unassigned</a>
</td>
</tr>
</table>
</td>
<td class="eight sub-columns last">12/12/2013 15:00:00 Shutdown Server</td>
<td class="expander"></td>
</tr>
</table>
</td>
</tr>
</table>
</td>
</tr>
</table>