Ben Nevis kilt-like pleated skirt, labeled US 10 but FITS LIKE A SMALL

My mom got this skirt for me in Europe. The sizing says US 10 but it fits me and I have a 27.5” waist and I wear a small so I would call it a size small/medium since it’s adjustable. It’s in really good used condition. The straps which look like leather are a bit cracked from use (see pictures). There is beautiful fringe detail down the side where it folds over. Good weight to the material. Not sure what my mom spent but she doesn’t buy cheap things!