[Christopher R. Rice]

I'm pretty sure that this goes back to the actual Explosive modifier here. The collateral damage for that attack would be 9d / (3 x distance in yards). So the targets within 10 yards take 9d if they don't dodge. Then targets at 10 yards take 3d, at 11 yards they take 2d, at 12 yards they take 1d, and so on. I'm sick, so that may be incorrect, but I'm pretty sure it's not. That said, Explosive 2+ is really better for small contained blasts that do smaller damage because they divide the collateral by a smaller amount.