You can use the "Set Movie Length" feature to set an approximate, desired video length. Magisto does initially set a default based on the footage uploaded, but you can always change it to your liking. Note that you may need to upload a certain amount of footage to be able to create video of longer length.
1) Tap the "Set Movie Length" button.
2) Drag the movie length slider to adjust the length as you see fit. You can use the “Short”, “Medium” and “Long” tabs at the bottom to make the selection a bit easier. Once you’ve arrived at your desired length, select Done to save it.
TIP 1: Remember that the maximum video length depends on the subscription you may have.
TIP 2: Note that the final video length is set during the video creation process, and the length set manually is an approximate length only.