Changing tick rate using the "/tick rate" command will alter any potion duration in its tooltip and the inventory timer of any active effects to reflect real time instead of in game time.

For example, a potion with an 8 minute duration, will display 16 minutes at half tick rate and 4 minutes with double tick rate.

The effect timer in the inventory will also change. After drinking an 8 minute potion with double tick rate, a 4 minute timer will be desplayed instead of desplaying an 8 minute timer that goes down twice as fast.