A Systems Force Flag Officer (SF-FO) commands a systems force from his stationing onboard its flagship...
A systems force must maintain control over dozens of inhabited star systems, typically consisting of multiple Star Destroyers and numerous other smaller capital & support ships. (In "real-life" terms, the typical operational systems force possesses between one and three Victory-class Star Destroyers with active officers onboard...) It is at this level that the command of a single officer may reach not only to a single warship -- but serveral -- including all officers stationed onboard!
This position is not a responsibility or status to be taken lightly. Certain SF-FOs may hold Division Command positions with Navy-wide administrative responsibility; and in lieu of such, a Flag Officer of a Systems Force is expected to devote significant "creative" attention to the formation and co-ordination of potential competitions, events, or other inspirations of activity involving their force.