A medium, typically a fluid, is supplied at a level of a rotatable body and is dispensed by a dispenser, such as a spray dispenser. The spray dispenser includes at least one spraying nozzle which applies a dampening agent to the roller. A spraying frequency of the spraying nozzle is adjusted with respect to a rotation frequency of the roller that is receiving the dampening agent. This makes it possible to avoid superposition of the dampening agent, at least for a defined number of rotations of the roller receiving the dampening agent.