The watch later list is like a "holding" spot for someone to watch the video. You will only get the view if someone watches at least 30 seconds of your video. The traffic will show up in your analytics "Browse Features" if it was watched from a viewers "Watch Later" list.
Here is a really good breakdown and understanding of where your traffic comes from (including the watch later) and how it shows up in your traffic.
The Reach tab in YouTube Analytics is your key to understanding how viewers find your content. It provides a quick snapshot of key metrics like click-through-rate, watch time, views, and more.
support.google.com
Hope this helps!