AN MD80 CREW; DSNDING INTO ATL; OVERSHOT A STAR ASSIGNED XING RESTR.

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FLT XXXX FROM MSP TO ATL. THE FLT WAS AT FL240 WHEN WE WERE CLRED BY ZTL TO CROSS ERLIN INTXN AT 13000 FT MSL; 250 KIAS. WE WERE THEN SWITCHED TO ATL APCH CTL. UPON CONTACT WITH APCH WE WERE INSTRUCTED TO 'CROSS ERLIN AT 13000 FT; DSND TO 9000 FT.' BOTH THE CAPT AND FO THOUGHT THE CLRNC WAS TO CROSS ERLIN AT OR BELOW 13000 FT; THEN CONTINUE TO 9000 FT. THIS WAS PROBABLY BECAUSE THAT HAS ALWAYS BEEN THE CLRNC IN THE PAST GOING INTO ATLANTA. THIS WAS THE FIRST TIME EITHER OF US HAD BEEN GIVEN A HARD ALT TO CROSS AT AN INTXN WITH A SUBSEQUENT DSCNT INTO ATLANTA. AS WE APCHED 1-2 MI FROM ERLIN; DSNDING THROUGH 12000 FT TO 11500 FT; APCH RESTATED THAT THE CLRNC WAS TO CROSS ERLIN 'AT' 13000 FT. HE ASKED US TO VERIFY OUR POS; BUT DID NOT WAIT FOR A REPLY. HE MADE A COMMENT LIKE; 'YOU GUYS NEED TO START LISTENING UP' AND THEN WENT ON TO GIVE OTHER ROUTINE INSTRUCTIONS TO OTHER ACFT. THIS GAVE US THE IMPRESSION THAT WE WERE NOT THE ONLY ONES TO DO THIS. NO CONFLICT WAS CREATED. WE CONTINUED DOWN TO 9000 FT AND CONTINUED ON OUR APCH TO ATLANTA. ALTHOUGH WE USE ROUTINE AND HABIT PATTERNS TO KEEP US SAFE (IE; CHKLISTS). THIS TIME THEY GOT IN THE WAY OF LISTENING FOR THE PROPER CLRNC. WE SHOULD HAVE VERIFIED THE CLRNC WITH APCH CTL. ON THE OTHER SIDE; ESPECIALLY IF OTHER ACFT WERE DOING THE SAME THING; APCH CTL COULD HAVE EMPHASIZED THE NEED TO CROSS ERLIN AT 13000 FT; 'THEN' DSND TO 9000 FT. AS MANY TIMES AS WE GOT INTO ATLANTA; IT IS EASY TO GET USED TO THE ROUTINE; AND THEN NOT NOTICE WHEN A SMALL CHANGE IS MADE TO THAT ROUTINE. OVER EMPHASIZING THE CHANGE WOULD HELP. SUPPLEMENTAL INFO FROM ACN 543714: CLRED TO CROSS ERLIN INTXN AT 13000 FT; 250 KTS; SWITCHED TO ATP APCH. INSTRUCTIONS FROM APCH CTL WERE CROSS ERLIN AT 13000 FT; DSND TO 9000 FT.