When applied to a ship of any type, this dictates how far the ship in question can travel without the need to refuel. On a ship design, this says how far it would travel on a full tank of fuel, however, when viewing this statistic of a fleet which is out in space somewhere, it simply is referring to how much farther it can travel before requiring refueling.

The range of a fleet reflects that of the ship with the least remaining range.

Range is calculated from the endurance of the ship's engine and the total weight. Small vessel drives trade range for thrust, only capital ship drives are suitable for long range travel.