Hello Adam

You can add or modify some lines of code in ../wp-content/plugins/wpdatatables/templates/admin/table-settings/table_settings_block.inc.php and around line 335. I'll show you an example how to add 12 and 52 in the list, and you can modify the code:

<select class="form-control selectpicker" id="wdt-rows-per-page">
   <option value="1">1</option>
   <option value="5">5</option>
   <option value="10">10</option>
   <option value="12">12</option>
   <option value="25">25</option>
   <option value="50">50</option>
   <option value="52">52</option>
   <option value="100">100</option>
   <option value="-1"><?php _e('All', 'wpdatatables'); ?></option>
</select>

This adds "12" and "52" in the Display tab above the table:

Then, open ../wp-content/plugins/wpdatatables/source/class.wpdatatable.php and around line 3207, add "12" and "52", so it looks like this:

$obj->dataTableParams->aLengthMenu = json_decode('[[1,5,10,12,25,50,52,100,-1],[1,5,10,12,25,50,52,100,"' . __('All', 'wpdatatables') . '"]]');

And the last thing to do is to go to line 498 of the same file, and modify it so it looks like this:

public function setDisplayLength($length) {
        if (!in_array($length, array(1, 5, 10, 12, 20, 25, 30, 50, 52, 100, 200, -1))) {
            return false;
        }

So, again, you only need to add "12" and "52".

This should work just fine.