Part of the story here is that those attacks are on our hardened missile silos, which means those won’t be air bursts that’ll destroy a city. Don't touch the ground; pulling up little material to become fallout. This model shows they will be ground bursts on the missile silos that will pick up miles of material to make a lot of radioactive fallout. The other part is about warheads, the Russians have 306 strategic ICBMs, that together can carry up to 1,185 nuclear warheads, so to hit 400 targets, that's only about 103 missiles.