ACR LGT ALT DEVIATION OVERSHOT DURING CLIMB.

Narrative

IT WAS A SHORT FLT FROM RDU-GSO. IT WAS THE FIRST FLT OF THE DAY. IT WAS DAY THREE OF A THREE DAY TRIP. BOTH DAYS BEFORE WERE X:OO AM WAKE-UPS AND THIS ONE WAS A X:OO AM WAKE-UP. WE WERE READY TO GET HOME. INITIAL CLRNC WAS TO 9000'. AFTER DEP WE WERE (WE THOUGHT) GIVEN 10000' AND SET THAT IN THE ALT REMINDER. LEVEL AT CRUISE (-10000') GSO APP ASKED IF WE WERE LEVEL YET. WE REPLIED 'YES LEVEL 10000'.' GSO APP SAID WE WERE ASSIGNED 9000'. THE CAPT (WHO WAS ON THE RADIO) SAID 'YOU GAVE US 10000; I READ IT BACK 10000'' THE CTLR SAID 'I'LL SEE IF RDU CAN TAKE YOU AT 10000.' NOTHING FURTHER WAS MADE OF THE INCIDENT. AS FE I WAS RESPONSIBLE FOR MULTIPLE DUTIES DURING THIS SHORT FLT; ONE OF THEM BEING ATIS FOR THE ARR ARPT. AS THE CLB CLRNC WAS GIVEN; I SWITCHED OFF GSO APCH FREQ ON MY INTERCOM SYS SO I COULD BETTER HEAR THE RDU ATIS FREQ. I NEVER HEARD IF 9000 OR 10000 WAS CORRECT. USUALLY I AM ABLE TO DO MY ASSIGNED TASKS; MAINTAIN TFC WATCH; AND WATCH THE TWO GUYS UP FRONT; BUT SOMETIMES THIS IS NEARLY IMPOSSIBLE; SUCH AS ON A 15 MIN FLT. SOMETHING HAS TO BE SACRIFICED. I DECIDED TO SKIP MY CROSS CHK OF THE PLTS ACTIONS AND A POSSIBLE ALT DEV OCCURRED. BEING TIRED AND 'GET HOMEITIS' WERE CONTRIBUTING FACTORS. I WAS SHOCKED TO SEE WHAT A MOMENTARY LAPSE OF PROFESSIONALISM CAN DO TO YOUR WHOLE DAY.