The "Opened" statistic is recorded when a User downloads or "opens" a hidden image within the phishing email itself. Within every phishing email that your target users receive we embed a hidden, transparent, 1x1 pixel .gif image at one of our URLs. When the target user's email client accesses the image from our server, we mark the user as having opened the email message. The ability to detect this "Opened" Statistic depends on the user's email client configuration. Apple (iOS) devices fetch remote images by default, for example.
Note: A Phishing Email can be considered "Opened" in the Reading Pane.