Hello jose
To edit these values you need some SQL skills.
The default values reside in the MySQL database Joomla uses.
You can edit the database tables using something like "MyAdmin"
http://www.phpmyadmin.net/home_page/index.php.
You can find out about the database name in your Joomla global configuration. The prefix mentioned in a previous post (#__) is replaced by a value of the global config as well.
Once you found out all of the above you can edit the default column values of the #__rsgallery2_acl table in the MySQL database of your Joomla install to match your needs.
Hope that helps
John
PS: In a feature release these values will be configurable form the back-end.