Edit video and audio in Numbers on Mac
By default, a video or audio file plays once when you click the Play button 
. You can set it to repeat in a loop, adjust its volume, and trim it to play only part of the video or audio. For a video, you can change the poster frame that’s displayed on a sheet to represent the video.
Set video or audio looping
Click to select the video or audio on the sheet.
In the Format
sidebar, click the Movie or Audio tab.To set media to repeat, click the Repeat pop-up menu, then choose how you want it to play:
Play in a continuous loop: Choose Loop.
Play forward and then backward: Choose Loop Back and Forth.
Note: Recorded audio can’t loop back and forth.
Trim video or audio
Click to select the video or audio on the sheet.
In the Format
sidebar, click the Movie or Audio tab at the top of the sidebar.Click the disclosure triangle next to Edit Movie or Edit Audio, then drag the Trim sliders.
Note: You can’t trim audio that you recorded in Numbers on your iPhone or iPad.
Change the poster frame for a video
You can choose the frame that’s displayed on a sheet to represent the video.
Click to select the video on the sheet.
In the Format
sidebar, click the Movie tab at the top of the sidebar.Click the disclosure triangle next to Edit Movie, then drag the Poster Frame slider.
Adjust playback volume
Click to select the video or audio on the sheet.
In the Format
sidebar, click the Movie or Audio tab at the top of the sidebar.Drag the volume slider.
You can set Numbers to optimise the format and quality of movies and images that you add to spreadsheets.