Please note, if you have been @mentioned in a Story on Instagram, and have then reposted the Story on your own account by clicking on "Add This to your Story", these reposted Stories are not included on the API, and therefore will not be included in your Stories analytics.
What does the Stories section include?
The Stories analytics tab includes information on how many Stories you've posted within a given time period, the total Reach & Impressions and average Reach & average Reach rate of those Stories. You can adjust the date-picker to get aggregated data on your Stories over a specified period of time. There's also a table that advises you on the best time to post Stories, and data on your average completion rate, and Stories with highest reach, Stories most completed, and Stories with most taps back!