
To change the length of a shot
For example, to make the selected camera shot active for a longer period of time, drag the bottom edges of the shot outward
                        to make the shot longer. The bottom corner numbers indicate the length of the shot. As you drag, the Scale cursor  appears.
 appears. 
                     

 or split
 or split  icon in the Camera Sequencer toolbar.
 icon in the Camera Sequencer toolbar. 
               The shot is split or trimmed at the current sequence time. Splitting a shot also splits the associated audio clip.