This analytic will provide you a set of information about the impressions made over time for the dataset. Impressions are calculated by the sum of follower counts for users who tweeted within a given time frame. Practically speaking, when a user with a follower count of 100 users tweets, those 100 users will have that user's tweet appear in their feed. When taken together, you can quickly get a sense of how many other people directly had access to a posted message. This is only an approximate value, however - it provides an inflated measure because there may be many mutually following users (User A tweets and User B tweets, each have 100 followers - if any people follow both A and B, the sum of the impressions should check against the union of the follower lists, instead it does not do this due to the excessive API calls involved). Additionally, even though a tweet can be fed to someone's feed, it doesn't really get "impressed" unless the person actually logs in and sees it. In talking about this data, then, it would behoove you to describe this value as the maximum number of people who could have seen the content that was posted at the time that it was posted.