The site section is basically used used to broadly segregate the different sections/content groups on your site. You can always manually add value (section name) to (s.channel variable) if you're completely sure about current tagging. If you're planning to dynamically capture and populate variable - Kindly tryhttps://theblog.adobe.com/getting-started-dtm-data-elements/ - Data Elements or get in touch with Web developer.
