Like others have mentioned, 50k small CPUs like 8085 can be made in a single production batch (i.e. a small basket containing silicon wafers, which passes through all manufacturing steps), so a number like this is likely to be the minimum amount that can be produced.

The customer would order this minimum quantity, and most of it will probably be kept as spares.

I assume the tooling and process are such that it’s a one-time thing, as in, this is the most of these chips that we could ever possibly need for all time. They’re not going to be able to spin up the same fab and build the same chips the same way again in the future whether that’s 5 or 50 years in the future. Given the long lifespans of military systems, it’s maybe not so crazy.

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.

I also am curious about that statement. Seems something got mixed up between the quantity of the full run and the quantity for the probe.