How to Edit video length iPhone 8 IOS 16.7.10

Trying to edit video length on my iPhone 8, iOS 16.7.10.

Apple Support webpage lists steps to trim a video on iPhone:, quote:

How to trim a video on your iPhone or iPad

1. Open the Photos app and tap the video that you want to edit.
2. Tap the Edit button.
3. Move the sliders on both sides of the video timeline to change the start and stop times. To preview your trimmed video, tap the Play button.
4. Tap Done, then tap Save Video or Save Video as New Clip.

I've selected the video. Tapped EDIT. Moved the slider on the left side of the video timeline to shorten the number of frames in the video.

"DONE" option at bottom of screen is greyed out. I am unable to save the changes.

What am I doing wrong?