Some Database Tables Have dr_ prefix
This can sometimes happen if you are using softaculous installer (or similar one-click installer provided by your web host). Perhaps you installed several instances of Drupal using the same database name, and just left the 'dr_' prefix in place for one by accident.

If I were you, I wouldn't worry too much about it. Having the additional tables there won't cause any problems with your Drupal installation (the one using the non-prefixed tables), and the 'dr_' prefixed tables won't increase in size as time goes on.

You should be able to safely leave them as they are, or, if you want to, remove them using phpMyAdmin to permanently delete (drop) the tables prefixed with 'dr_'.