From Creatures Wikia
This agent adds a panel to the left of the screen that displays various information about your creatures, including their name, sex, age, life stage, generation, and if they have been through the warp. In addition to this it checks for possible immortal and fast-aging creatures. Clicking on the "O" will flag any creatures who are older than 9 hours, which may be immortal. Activating the "T" will check for immortal Creatures by looking for any which have two or more toxins at 95 or more. Grendels are exempted from this check. Finally, the "A" will check for Fast Aging creatures by comparing their hatching time stamp to the time they reach adulthood. Any creatures which fit the criteria for Old, Toxin or Aging will be marked with the appropriate letter.
The information is updated about every 15 seconds. Which species to check (Norns, Ettins, Grendels, Geats or any combination of these) can be chosen by highlighting the buttons on the right side. The statistics at the bottom of the panel show the current number of living males and females of each species and the highest generation present. The up/down arrows allow you to scroll through multiple pages of entries.
Norn Statistics is also aware of Medical Monitor - whichever is installed first will be positioned lowest down on the screen.