AN A320 CLBS ABOVE ITS ASSIGNED ALT WHEN THE CREW MISREADS THE CLRNC 40 MI NW OF PHL; PA.

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ON CLBOUT FROM PHL WE WERE GIVEN A CLRNC TO A HIGHER ALT. THE FO WAS FLYING AND I UNDERSTOOD THE CLRNC AS 'CLB TO FL270;' THE FO PUT FL270 IN THE ALT WINDOW. I WAS AT THE TIME PREPARING TO CALL BACK THE TIMES TO PHL OPS. BEFORE I LEFT THE FREQ; I CONFIRMED THE ALT WITH THE FO AS FL270 AND HE CONFIRMED FL270. WHEN I RETURNED TO THE FREQ THE FO STATED THAT AS WE PASSED FL192; ATC CALLED TO CHK OUR ALT AND STATED THAT WE WERE ONLY CLRED TO 17000 FT AND THEN SAID 'NOW YOU'RE CLRED TO FL210' AND WE CONTINUED TO CLB TO FL210. THE WX WAS CLR WITH VISIBILITY UNLIMITED AND THERE WERE NO CONFLICTS. I CANNOT TELL YOU EXACTLY HOW THIS OCCURRED; BUT I CAN IDENT CERTAIN ELEMENTS INVOLVED. 1) THE CREW WAS OPERATING VERY EARLY IN THE MORNING WITH REGARD TO OUR OWN TIME ZONE. WE WOKE UP EARLY MORNING WEST COAST TIME. IT'S DIFFICULT TO GET A GOOD NIGHT'S SLEEP WHEN YOU HAVE TO TRY TO GET TO SLEEP SO EARLY WITH REGARD TO OUR OWN TIME ZONE. 2) THE FLT WAS #2 YYY; WE WERE APPARENTLY CLRED TO 17000 FT AND FL270 SOMEHOW WAS PLACED IN THE ALT WINDOW ON THE FCU. SUPPLEMENTAL INFO FROM ACN 438953: I WAS BUSY WITH MANUALLY TUNING VORS AND RADIALS TO VERIFY A PLACE BEARING (FMS PROC) INTERCEPT CLRNC.