In the source tweet_url table, there is am index field, which refers to the URL's place amongst the list of URLs included in a tweet, as a tweet may include multiple links. In the package's twitter_ads__url_report model, however, in order to maintain the integrity of aggregated metrics at the URL grain, we have chosen to only report on the first URL in a tweet. We've chosen the first one specifically because a tweet with multiple links will only showcase a link preview-box for the first URL.