The computer tally was used on Isla Nublar to keep track of all the dinosaurs on the island. It relied on motion sensors that covered 92% of the land area of the park. The computer compared the animals found by the motion sensors with the expected number of that type of dinosaur. If the count was off, if the creature had left the area or stopped moving, it would signal an alert. John Arnold used the computer tally as an example of Jurassic Park’s superb security system. 
The expected number of animals was 238, and the computer would not search for more than that, as it was assumed that there couldn’t be more. (computer tally with the expected 238 animals at left)
Ian Malcolm used the computer tally to prove that the dinosaurs were breeding. He had the computer search for 300 animals, and it found 292-proof that the original 238 dinosaurs were breeding. (computer tally with the total 292 animals at right) The inability to search for more than the expected number of animals was one of the fatal flaws in the security system of Jurassic Park, as park staff failed to notice the breeding dinosaurs until it was too late.
