The small graph symbol (located in the "Keywords Analysis", "Competition Analysis" or "Keywords Monitoring" tables in the "Rank" column) provides you with your app's ranking history on any given keyword (in comparison with your competitors if you've added some).
The default date range is the last 90 days. You can choose other date ranges or create your own.
Important: our tool provides you with Keyword Ranking History since the day the keyword was first tracked on the tool (by you or any other user). If it's a brand-new keyword (that was never tracked before on the tool), we may not have any data yet and, therefore, the history will start from the day you've added this keyword to your Keywords Analysis.
It can also happen that you or a user stops tracking that keyword and then start tracking it again. You will therefore have a "hole" in the data.
Therefore, to make sure to always have the daily updated rankings for a given keyword, make sure to add & keep it tracked in your Keywords Analysis.