Well, we could try to modify it, although even we ourselves are not sure if this is going to work after the next update.
Go to your plugin settings, find & select the settings.php file, and change the 525 line from the following code:
<option value="30" <?php selected($options['max_related_post_age_in_days'], 30); ?>>1</option>
... into this one:
<option value="14" <?php selected($options['max_related_post_age_in_days'], 14); ?>>14 days</option>
Don't forget to click on the 'Save' button and when the plugin updates, don't mess with the file again. (Or do, if this line of code changes again.)
Let me know how it goes or if you need any additional assistance — I'll gladly help! Here's my email address: email@example.com
Take care & have a nice day!