Explanation of ItemInfo.shn > UseClass numbering system

Hey all, question here.

In ItemInfo.shn > UseClass column, I attempted to alter the required class of an item.
Degro Armor (Normally for warrior) - however its number is set to 4, which according to ClassID is Gladiator. I was a little confused and changed the number to 1, for Fighter.

This made the item class 'Common'

Any explanation on this?

- - - Updated - - -

Im dumb I know how I can figure out the numbers to what class.
Still weird that it doesnt match Class ID tho

UseClassTypeInfo.shn - look at that one for the Item Class :P

Yea I made a list, its just super dumb that its not the same as the ClassID