Structured data markup is a standard way to annotate your content so machines can understand it. When your web pages include structured data markup, Google (and other search engines) can use that data to index your content better, present it more prominently in search results, and surface it in new experiences like voice answers, maps, and Google Now. Read more

Telling theme adds structured data to your content out of the box, which is intended mostly for blog posts. There are couple of things to note to fully benefit from this feature:

  1. According to Google’s rich snippets guidelines for articles, at the time of writing images should be at least 1200 pixels wide, and images should be in .jpg, .png, or. gif format. So you would want to make sure that your featured images for articles meet minimum size requirement. If you do not have featured image, make sure to add default image in Theme Options/Blog settings. If your images are smaller than recommended size, they will still be added to structured data and no error will be shown, however it is always better to follow recommendations.
  2. Google’s rich snippets guidelines for articles require publisher name and logo. The logo is set in Theme Options/Header Options/Meta Logo.

    The logo should should be at least 112x112px.

Websites can be tested for structured data markup here: https://developers.google.com/structured-data/testing-tool/.