I'd forgotten to also mention that for many classes, Jackill
lists a number of vessels that are merely proposed additions to that class. So for a design that has maybe a hundred ships listed total, the actual number in service might only be half of that. Whereas with the Jenghiz design, the high number makes some sense because it's implied to represent all of the FJ era destroyers (the Saladin class and its three variants). This seems pretty fair and logical to me, and I've seen similar notations in other works regarding vessels that are under construction or proposed but not actually commissioned into service.