Is the same 4items Abstract Sunflower Embroidered Skirt? Why would that be? Is that a glitch. Could it be fixed?

You don't get 4 skirts, you just get one.

This seems to happen for every achievement where there are tiers and prizes for earlier tiers, but no prize for a later tier. The last "prize" up seems to show up for the next level if there is no star. It also happens with: Melody Regular, Wizard Employee, Plushie Collector, Trading Card Collector, Filled Wardrobe - also happens at the 8K level, Gourmand, Big Spender, Token Shop Regular , Linkback Buttons! and Making a living.