While making a video in the Vimeo Android app, the Vimeo iOS app, or the Create apps for Android and iOS, our engine will automatically decide on a length for your video based on the media you’ve chosen.
Your uploaded footage will determine the length of the video itself. Images are automatically set at 2 seconds each.
You can also change the duration of the video manually. You can read more about using the timeline to change the duration of a video at 'How do I use the Timeline in the Vimeo mobile apps? '.