What is '__SUPER_ADMIN_GID', 25 used for?

[Rixters]

We are developing a new site in VM and I cam accross the following code in: administrator/components/com_virtuemart/models/user.php

    // Hardcoded groupID of the Super Admin
    define ('__SUPER_ADMIN_GID', 25);

Where is this define used and does is have to be 8? We are usinh Joomla 3.4.1 with VM 3.0.8

Hope someone can point me in the right direction...