Equip Enhance

Equip Enhance refers to the ##% you see next to the stats on your weapon. It
represents the effectiveness of the weapon over a standard weapon of that type.
For example, a Bronze Bow bought from Chulsan has 42 durability. No matter
what, if you purchase a Bronze Bow from Chulsan, it will have 42 durability.
Now, if you find a Bronze Bow from a water ghost, and it happens to have 46
durability, you'll see the durability stat stated as follows:
Durability 46/46 (+10%)

~~~How to utilize Equip Enhance~~~
-Press A to bring up the action window, then right click the alchemy icon.
-Press the Equip Enhance tab to open up the Equip Enhance window.
-Place the item on the left side of the Equip Enhance window.
-On the right side of the Equip Enhance window, place an Intensifying Elixir of
the appropriate type (Weapon for Glaive/Bow/Sword, Protector for protector type
armor, etc.)
-Lucky Powder and the Lucky trait are both utilized in Equip Enhance, just as in
old alchemy.
-Press the fuse button, and hope you don't fail.

~~~Failed Enhance Attempts~~~
-If you fail, the enhance level of the equipment resets. Not good.
-If you fail a +5 or higher, the item may be destroyed or its durability
reduced.
-Each successful Equip Enhance reduces the chance that any further alchemy will
be successful.
http://www.gamefaqs.com/computer/doswin/file/930711/43300