That number was probably shaped by minimum production-run requirements, alongside the need for software development units, along with other factors, like the use in Trident II and other quests we may not know about.
> other quests we may not know about.
Back then an interface between terrestrial computer systems and a Zeta Reticulan spacecraft required a small supercomputer on our side.
There isn't really a minimum production run for silicon chips, they do small test runs all the time to test new designs.
At least not from a practical perspective.
From an economic perspective, stopping after a single small run is just wasteful. The upfront design costs are so high, and the per wafer costs are so slow that you might as well make a lot extra. Maybe you can find a use for them, or sell them to someone else.