The data returned comprises the download URLs for the catalog feeds starting from the latest full feed and therefore depends on the date when the request is made.
E.g., if the request is made on the day when the full feed was generated, then the response will contain only the link to the full feed. However, if it is made several days after, it will contain both the link to the full feed and the links to all the feeds with incremental updates generated since the last full feed.