Question concerning Impact weapon Enchant

[Andrew Ahrens 896]

According to the magic weapon enchant table I am looking at Impact has a little 3 with it which the table says that means it can only be on slashing or piercing weapons.

Looking at the description it honestly feels like it should be a bludgeoning enchantment so should the number be a 2 which is bludgeoning only thus this a misprint or should it not have 3 or 2? If it is suppose to be P or S only why is that the case?

[Gisher]

The description of Impact doesn't mention restrictions based on piercing, slashing, or bludgeoning. Instead it says that Impact can't be placed on light weapons. Because of that, I've always assumed that the 3 was supposed to be a 4.