This is the sum of increases or decreases in followers during the selected date range.

This allows you to easily see at a glance the number of follower change per day, week or month! Monitoring the days with the most significant increases or decreases in follower amounts can give insight into which content is attracting new follows and which content triggers unfollows. 

Your Growth of Total Followers data is available for business accounts for up to two years back or since the account was converted to a business account.