A DSNDING HS25B OVERSHOT ITS ASSIGNED ALT ON A STAR ARR. CREW WAS UNDER THE IMPRESSION THAT 11000 FT WAS ASSIGNED.

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AT APPROX XA45 ZKC; ON FREQ 134.50; ISSUED A CLRNC TO CROSS THE KAYLA ARC AT 11000 FT. AT THAT TIME; WE WERE CLRED TO STL VIA THE TRAKE 8 ARR BUM TRANSITION. AFTER A SHORT VECTOR AROUND THE TRAKE INTXN WE WERE ESTABLISHED ON THE FTZ 265 DEG RADIAL INBOUND AS DEPICTED ON THE STAR. THIS IS MY BEST RECOLLECTION OF WHAT HAPPENED LEADING TO OUR ALTDEV. ACFT: CROSS WHAT AT 11000 FT? ZKC: THE KAYLA ARC. ACFT: CROSS THE KAYLA ARC AT AND MAINTAIN 11000 FT. ZKC: CROSS THE KAYLA 11 DME ARC AT AND MAINTAIN 15000 FT. ACFT: I'VE GOT IT NOW; CROSS THE KAYLA 11 DME ARC AT AND MAINTAIN 15000 FT. WITH THE XING BEING THE 11 DME ARC; MY READING BACK 11000 FT TWICE AND THE FIRST ALT NOTATION ON THE STAR BEING 11000 FT; I SET THE FMS AND THE ALT PRESELECT FOR THE DSCNT TO 11000 FT. AT THE BEGINNING OF THE DSCNT; I ADVISED ZKC WE WERE DSNDING FROM XXXXXX TO 11000 FT. I DO NOT RECALL HIS RESPONSE; IF HE DID; BUT I KNOW I WAS NOT CORRECTED. ONCE IN THE DSCNT; I SWITCHED TO UNICOM TO ADVISE THEM OF OUR ARR. WHEN I RETURNED TO THE ZKC FREQ; I HEARD THE PF SAY; 'WE READ 11000 FT BACK TWICE.' WE WERE AT 12000 FT. I REALIZED THE ALT WAS 15000 FT AND ADVISED THE PF OF MY ERROR. WITH ZKC PERMISSION AND COORD; WE CONTINUED TO 11000 FT WITHOUT INCIDENT. THE ISSUANCE OF THE CLRNC TO CROSS THE 'KAYLA ARC' APPEARS TO BE NONSTANDARD TERMINOLOGY OR SELDOM USED AT BEST. EVEN AFTER BRIEFING THE STAR; IT DIDN'T SOUND RIGHT THE FIRST TIME THE CTLR ISSUED IT TO US. HAD THE CLRNC BEEN; CROSS KAYLA AT 15000 FT; OR CROSS THE FORISTELL 11 DME ARC AT 15000 FT; THE CLRNC WOULD HAVE BEEN CLR AND CONCISE. TO MIX THE INTXN; ARC AND VOR TERMINOLOGY JUST CREATED CONFUSION. I BELIEVE THIS IS SUPPORTED BY THE FACT THAT 2 EXPERIENCED PLTS COMPLETELY MISSED THE ACTUAL CLRNC. SUPPLEMENTAL INFO FROM ACN 426418: DID THE CTLR MEAN ONE THING AND SAY ANOTHER?