The additional fields include the title of the series, season and episode numbers for the particular video and the premiere date as well as other information. According to the post, your video's metadata will help Google in providing more details and relevancy to users who searches for your show online.

The post also included an example Video Sitemap entry explaining the correct code as given below:

<video:video>


    <video:title>The Sample Show, Season 1, Episode 2</video:title>

    <!" other required root level video tags omitted ">

    <video:tvshow>

       <video:show_title>The Sample Show</video:show_title>


       <video:video_type>full</video:video_type>

       <video:episode_title>A Sample Episode Title</video:episode_title>

       <video:season_number>1</video:season_number>


       <video:episode_number>2</video:episode_number>

    </video:tvshow>

</video:video>

You can find the complete documentation for the tags (both mRSS and Video Sitemaps) at the Webmaster Tools Help Center. For any queries, you can go to the Webmaster Help Forum's Sitemaps section.