Visitors - number of unique visitors on your website
Engaged Visitors - number of unique visitors who saw at least one notification
Engagement Ratio - ratio of users who visited your website and saw at least one notification
Impressions - number of times your notifications have been viewed (7 day unique impressions)
Hovers - number of visitors who hovered your notifications (7 day unique hovers)
Clicks - number of visitors who hovered your notifications (7 day unique hovers)
CTR - ratio of users who saw a notification and clicked on it (clicks divided by impressions)