Is this for a OJS 3.x install, or a OJS 2.x install?
The usage and options for this configuration setting changed between 2.x and 3.x:
Regardless, depending on what point you copied your config.inc.php from config.TEMPLATE.inc.php, and what upgrades have happened since then, your config.inc.php may have diverged from the lasted options and comments in config.TEMPLATE.inc.php.
As part of each upgrade, I make a habit of redeploying the config.inc.php settings into a fresh copy from config.TEMPLATE.inc.php, so that any comments are updated and new settings are reviewed.