The program was written in such a way that it expected a certain number of dinosaurs in a paddock and returned a successful result when it reached that number. However, once it reached the threshold, it did not count more dinosaurs. Once modified, the program outputted the correct total, thus identifying that the dinosaurs were producing offspring in a single sex environment.
Take a look carefully next time you are in a zoo. No active electric fences, lots of very dangerous animals, all contained. Dinosaurs would be almost no different.
It's a clear case of "but then the movie wouldn't happen".
As a bonus round, note the strange absence of guns as a final fallback and the blitheringly idiotic reasons deployed that they don't exist, can't be used, or don't work somehow. Granted, you need more than a .22 in case of emergency but this has been a solved problem for over a century.
The first movie I still enjoy even so. I don't let this interfere with my enjoyment of a cinematic classic, and rich eccentrics hiring the totally wrong people who overconfidently do everything wrong I can track with. The sequels, especially the ones with more parks, I have a much harder time with. Jurassic World really should have worked just fine, at least up until the volcano hit. And I don't mean worked fine as-is, as it is also disastrously misdesigned. I mean, a real, correctly designed park is certainly not "easy", but well within reach for a modern corporation even remotely concerned about liability.