In Motion, do one of the following:
With the timing display set to Show Project Duration, double-click the number, type a duration value, then press Return.
When the timing display is set to Show Timecode, you can type a precise timecode value in the HH:MM:SS:FF format (hours:minutes:seconds:frames).
With the timing display set to Show Project Duration, drag left or right over the number to decrease or increase the duration.
Choose Edit > Project Properties (or press Command-J), then change the value of the Duration field in the Properties Inspector.
Note: Click the down arrow to the right of the numbers in the timing display and choose Show Frames or Show Timecode to switch between viewing the project duration in frames or timecode.