Please review the ePO 4.5 help topic - 'How a system is first placed in the System Tree' which explains in detail the process ePO follows to sort a system into the proper group in the system tree.
You can get to this topic by drilling down the path in the help window: 'McAfee ePolicy Orchestrator 4.5-->Organizing the System Tree-->How a System is first placed in the System Tree'.
Hope that helps.
Thanks you for your answer. That worked.