is this even talking service account or is it talking about this page: sharepoint:666/.../Default.aspx ? (some info changed to protect the innocent).
it says:
Set sharepoint Administrator Group Account
Specify the Windows NT security group account to which you want to grant administrative access for SharePoint Products and Technologies. Members of this group do not have to be local administrators to perform administration tasks for SharePoint.
Note that members of the local Administrators group can also perform administration tasks for SharePoint Products and Technologies.
and currently i still have it at the default setting of my service account.