It says "Fireball radius: 0 m" for me. Did you click the 'Detonate' button? It's not one of those things that updates as you type.
> Estimated fatalities: 6,010
> Estimated injuries: 8,060
> In any given 24-hour period, there are on average 28,743 people in the light (1 psi) blast range of the simulated detonation.
vs. a Davy Crockett in the same location:
> Estimated fatalities: 4,130
> Estimated injuries: 2,790
> In any given 24-hour period, there are on average 12,248 people in the light (1 psi) blast range of the simulated detonation.