A single video's result is also shaped by the topic, the packaging, and when you published it. Only a run of several videos shows whether the change in length did anything.
How long does it take to see whether a change in video length worked?
Track the change over the next few weeks. One shorter video that worked out proves nothing on its own.
Related questions
What should you do when viewers leave halfway through a video?
Is it worth splitting a long video into several shorter ones?
Does a longer video always mean more watch time?
How do you know what length fits your niche?
How do I find YouTube video ideas that actually work?
Does changing topics hurt a YouTube channel?
See all questions