[MauranKilom]

72 hours are 259200 seconds.

Playing 4.9 million matches of ~100 plies each at 0.4 seconds per ply is 196000000 seconds.

That's < 1000 TPUs. Sounds big but not too-large-for-google big. But other comments here say that the 0.4 second number is also wrong (and in fact significantly lower).