I get that. The conventional test at alamagordo was 110 tons and the blast was heard 60 miles away. This would have been a hell of a bang at 60k tons notwithstanding 600k tons.
Could very well be the gross weight of the munitions that were involved, casings etc, not the HE.
I concede that the total weight more than likely was all of the ordnance combined but as I heard the story at Picatinny (they have a small museum there), the main detonation was at a bunker filled with a very large quantity of old TNT.
I am more than acquainted with large-scale detonations: I participated in several nuclear tests and nonnuclear simulations using ANFO. And no, 600kt at surface wouldn’t “destroy all of New Jersey”. Newark, maybe, (as if it isn’t already destroyed) not all New Jersey. This even acted like a very, very large surface nuclear event, minus the thermal and the direct Gamma.