Duration
Source Player Core pg. 418
Most effects are discrete, creating an instantaneous effect when you let the GM know what actions you're going to use. Firing a gun, moving to a new space, or taking something out of your pack all resolve instantly. Other effects instead last for a certain duration. Once the duration has elapsed, the effect ends. The rules generally use the following conventions for durations, though spells have some special durations.
For an effect that lasts a number of rounds, the remaining duration decreases by 1 at the start of each turn of the creature that created the effect. Detrimental effects often last “until the end of the target's next turn” or “through” a number of their turns (such as “through the target's next 3 turns”), which means that the effect's duration decreases at the end of the creature's turn, rather than the start.
Instead of lasting a fixed number of rounds, a duration might end only when certain conditions are met (or cease to be true). If so, the effects last until those conditions are met.
Some effects can be ended early with the Dismiss action. An effect with the sustained duration lasts until the end of your next turn, but it can be extended as described in the Sustain action.
For an effect that lasts a number of rounds, the remaining duration decreases by 1 at the start of each turn of the creature that created the effect. Detrimental effects often last “until the end of the target's next turn” or “through” a number of their turns (such as “through the target's next 3 turns”), which means that the effect's duration decreases at the end of the creature's turn, rather than the start.
Instead of lasting a fixed number of rounds, a duration might end only when certain conditions are met (or cease to be true). If so, the effects last until those conditions are met.
Some effects can be ended early with the Dismiss action. An effect with the sustained duration lasts until the end of your next turn, but it can be extended as described in the Sustain action.