I personally take the number of views from subscribers within the first 48 hours of releasing a video. If that number is high, you know your subscribers really enjoy your content and will watch as soon as they can. However, if that number is low, there's a good chance that your content is swaying away from the type of content people initially subscribed to watch. It also caters into the theory of "view velocity," where your content has a greater chance to be placed on browse features if there is a solid amount of your subscribers returning to watch a new video.