In a design containing both video and audio clips, video will determine the duration of the design. If you want to use audio duration, turn on the ‘Use Audio Duration’ option. This will set the video duration to that of the audio. This may cause the video to either trim or loop, depending on the length of the audio.
By default, the audio will play according to the video duration, so the audio may get trimmed for a short duration video, or played in loop for a long duration video.