stock 1999 suzuki katana GSX600F rear Shock Adjustment

[Blueberry]

hey I知 new here and to the motorcycle world so I知 wondering if anyone would happen to know what the adjuster Dial on top of my stock 1999 suzuki katana GSX600F rear Shock is used for any and all help and information would be greatly appreciated I have pics of what I知 talking about but for some reason I can稚 add them to this

[MNkat]

These allow minor adjustment to the rebound damping.

[RickHX]

These allow minor adjustment to the rebound damping.

My uncle recently acquired a Katana GSX600F and the shocks are a little stiff. Gonna check the shock adjustments when start working on it next week, just need to finish installing the rack and tonneau covers on the truck before we can clear the garage.