rSeries and Active Directory authentication

Hello
Im trying to configure Active Directory authentication with rSeries 4800

Tried to follow this guide:
https://techdocs.f5.com/en-us/f5os-a-1-0-0/f5-rseries-systems-administration-configuration/title-user-mgmt.html

I configured all but this: "Assign users to valid system group IDs on the external LDAP or Active Directory servers. For more information, see the Group IDs and system authentication roles section."

I have no idea how to assign the F5 group ID (f.e. Rolename Admin with GID 9000) in Active Directory and it is not explained in the documentation.
Without doing it the authentication its not working so Im assuming this setting could be the reason.

Any help would be appreciated