Ghost Scope Range

My understanding was originally that the visibility settings of a mission determined the range, around each client, at which objects would be ghosted to a client. However, further tests have shown this is not the case.

Where can I adjust this range?

If the engine calculates this as "visibility + X = range", which would make sense as that would allow the objects to be ghosted before they come into visibility range, where in the engine is this number set?