I (native speaker) read it as cutting 3000 of the 4500 managers (keeping 1500) of the engineering arm. Of those 3000, ~1400 will move to an engineering position (probably because they are actual engineers promoted to management) and the rest is let go.

ASML wil zo’n 3000 van de 4500 banen van managers in de engineeringtak laten vervallen. De verwachting is dat ongeveer 1400 mensen een nieuwe functie als engineer kunnen gaan vervullen. „Van ongeveer 1700 mensen verwachten we afscheid te moeten nemen”, stelt financieel topman Roger Dassen in een toelichting.

If I were a betting person, I'd bet that's the number of engineers who were previously forced to become managers in order to get a promotion.

I've worked with a number of people who made the IC -> manager conversion because it was represented as the best way forward in their career, only to find out it made them miserable, and convert back after a few years. I think you'll find that sort of conversion back to IC is not all that uncommon.