Articles in the RSS feed are fetched during the generation of the digest.

The number of articles fetched depends on the value of Max Items Per RSS Feed in the plugin settings page. The time range of the fetch depends on the Time Span value in the reading source editing page.

For example, if the Max Items Per RSS Feed value is 10, and a particular reading source's Time Span value is set to 1 day, then this reading source will retain a maximum of 10 articles (which could be fewer than 10, as there might not have been 10 articles published in the past day).