A higher level of this skill reduces the number of...
A higher level of this skill reduces the number of zeros you deliver on your opponent.
If you want your attack level to progress faster just wear an amulet of power and start fighting.
Another way to increase your attack is to wield the correct type of weapon,
Like if your attack level is 1 use an iron scimitar instead of the bronze or training one.
I would recommend a scimitar as it is balanced

Metal	Image	Attack level
Bronze		1
Iron		1
Steel		5
Black		10
Mithril		20
Adamanite		30
Rune		40
Dragon		60