If you write a summary in e.g. a press release, the summary will not be shown in the actual publication.
The summary will be displayed in list views, like for example search engine results, social media feeds or on Mynewsdesk Stories (http://www.mynewsdesk.com/se/stories). Moreover, it will be included in the email alerts which are sent out to followers of categories.
If you want the summary to appear in the press release, you will also have to include it in the body text, for instance as a preamble.