Show us a ss of the item itself.  This is saying you have already used the selected glyph and gotten as good a value as you can get with that * glyph on that particualr substat.

you are probably trying to enchant a substat with a glyph right?

It seems that you have reached the maximum amount of bonus the Glyph can give you. If it is anything below a 6* Glyph on a 6* Piece, you may want to try a higher ranked Glyph. If it is 6* then thats the Limit and you cannot upgrade it any further.

Hope that helps!

So here's the weird part though - how is he able to upgrade if it's maxed? The UI doesn't even allow you to use it.