The directive "specify one suburb only" means you must select and provide information for a single suburban area—not a list, not multiple, not the whole city. A suburb is a residential district on a city's outskirts. For example, if a form asks for your suburb and you live in Greater Sydney, you'd write "Parramatta" or "Bondi"—not "Sydney" and not "Parramatta, Bondi, Manly." It ensures precise, unambiguous geographic data for mapping, demographics, or service delivery.