I'm going to use a sample from Genesis mod to help me ask this.
[ATTACK:EDGE:5000:1950:slash:slashes:NO_SUB:1300
What do all of the things I have bolded mean?
The 5000 is contact area. If I understand it correctly it's the amount of area struck by the weapon. Like how big the end of a warhammer is for example. Not entirely sure how this effects bladed weapons, but I'm almost certain it does.
the 1950 is penetration. I believe that is only used with edged weapons. It's the size of the weapon's point. The larger the point the easier to hit organs or chop limbs like a sword or axe. The smaller the point the better it is at penetrating through armor and hard materiels like a spear or arrow.
1300 is the velocity multiplier. I'm not sure exactly how that works, but generally a higher number is a harder hit. It probably represents something like the leverage that can be applied to the weapon. I think that 1000 is "normal" with no additions or subtractions, but I don't have a source on that.
(Another thought that can be applied to the velocity multiplier is that it is how much the user's velocity factors into a strike. Making a charge inflict more damage. But these are two different thoughts and I'm not sure anybody tested which one it actually is, or if it is both of them. I think it's the first one myself, but I added this for the sake of completeness.)
The numbers in ammo are identical in meaning to other weapons. Though they tend to have a much smaller size and penetration.