What does 'PO' on the control panel display mean?

PO stands for Power Outage and indicates that the power supply to the refrigerator has been off and the freezer temperature has risen to 18°F (-8°C) or higher. An alert tone will sound three times and 'Confirm' will blink on the display until you acknowledge the power outage by pressing MEASURED FILL under 'Confirm.' Once confirmed, the 'PO' will disappear and the display will return to the Home screen. (Page 22)