[Pre-BB] MapleStory Formula Compilation

Power Knock Back (both weapons, credit to AGF/Fiel):
MAX = (DEX * 3.4 + STR) * Weapon Attack / 150
MIN = (DEX * 3.4 * Mastery * 0.9 + STR) * Weapon Attack / 150
Mastery is 0.1 at all levels

Where is this mastery come from?
Does it depend on Bow/Crossbow mastery?

Or

Does it depend on skill level as in
power knockback is level 30 = mastery 0.1 + 0.3 ?

Or

Mastery is always 0.1 , doesnt depend on any skill nor factor.
If its so, then remove the word mastery and replace with 0.1

Can I just ask how you misinterpret "mastery is 0.1 at all levels" to in fact mean something else? It says right there that it's 0.1, I think that's a better explanation than just having a random 0.1 in the formula and not saying why it's 0.1 or anything.