Increased frenzy damage?

My character tab still shows "4% MORE damage" per frenzy charge even after equipping it. So this is probably bugged.

But how does it work? Will it increase damage from 4->10 or will it increase 4->4.24?
If it's the 2nd method, then it's kinda useless. But if it's the first, it's kinda op. So I guess it's the 2nd?

Also does it even work? Is only the GUI bugged or is this entire enchantment bugged?

Increased gets added to all your other sources of increased. More is a multiplier. The 4% more damage per charge doesn't change. But if you have 500% increased damage and then get 4 frenzy charges, you'll have 524% increased damage to go along with the 16% more damage. The wiki can probably explain more/less and increased/reduced damage modifiers better than I.

I know how damage modifiers work I just didn't know how this particular one works. Because the "increased" could be applied to the "more". As in "increased MORE damage". But it just adds increased damage.

So basically it adds 6% increased damage to your total 'pool' and not the the charge itself. Making this modifier relatively useful at more charges but not very strong compared to a +40% damage enchantment unless you have perma 7 frenzy charges. Thanks.

"increased frenzy damage" means that it is, first, increased damage(not "more" itself and not a modifier to FC's "more"), and second, it applies only to Frenzy skill. Just judging from wording of all other similar enchants.