WPMU DEV dashboard access for all admins

How come I can only see the WPMU DEV dashboard inside my WP Dashboard when I am the main user?

I have created other admin accounts and for some reason I am not able to see the WPMU DEV dashboard when logged in to the other secondary admin accounts.

I see if I want to give access to the WPMU DEV dashboard to other admins I have to add this code to the wp-config.php fil.

define('WPMUDEV_LIMIT_TO_USER', '1'); or
define('WPMUDEV_LIMIT_TO_USER', '1, 12');

How do I find the UserID for each admin?