Seven of Nine, Tertiary Adjunct of Unimatrix Zero One, is of course the most well known Borg designation. But what do these designations actually signify?
Is the Unimatrix number indicating a region of space, or her group of 9 drones? Memory Alpha says the term is used interchangeably. Due to all the qualifiers (Tertiary Adjunct), there must be millions or billions of drones designated as Seven of Nine throughout the entire Collective.
Was she the equivalent of 3rd Officer for her group of 9? Or for Unimatrix Zero One, whatever it was?
It seems like the meaning of designation was purposely left vague, maybe just to drive us crazy thinking about it.