How to set the range
If you do not want the clip to start at the beginning of the source video, set to Custom, then play through the video to locate the beginning point. Use the play, slow motion and fast forward buttons to move through the video. Always use the red stop button between commands.
Click on the red exclamation mark to set the current position as the beginning of your clip.
Then specify the end point in the same way.
To check that the beginning or endpoints are correct, stop the video with the red stop button. Click on “locate” for the beginning or endpoint. Then click the play button.