Air carrier first officer believes controller issued a descent to 6000 ft rather than 8000 ft.

Attributes
ACN	454794
Time
Date	199911
Day	Sat
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : rdu.airport
State Reference	NC
Altitude	msl single value : 6000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : rdu.tracon
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	descent : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : cfi
Experience	flight time last 90 days : 70 flight time total : 5500 flight time type : 320
ASRS Report	454794
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : published procedure
Independent Detector	other controllera
Resolutory Action	controller : separated traffic flight crew : returned to assigned altitude
Supplementary
Problem Areas	Flight Crew Human Performance ATC Human Performance
Primary Problem	Ambiguous

Narrative:

Checked in with approach control. ATC gave heading and altitude instructions. A northeast heading was issued and an altitude of 6000 ft was given. I read back leaving 11000 ft for 6000 ft. 15 mi later, ATC said we should be at 8000 ft and told us to climb back to 8000 ft. I know I was correct with the clearance because of the agreement with the captain. ATC read back, and altitude selector set at 6000 ft. ATC may have thought he was working another sector. He could have been tired or he may have been loaded up with too many planes to control.

Original NASA ASRS Text

Title: ACR FO BELIEVES CTLR ISSUED A DSCNT TO 6000 FT RATHER THAN 8000 FT.

Narrative: CHKED IN WITH APCH CTL. ATC GAVE HDG AND ALT INSTRUCTIONS. A NE HDG WAS ISSUED AND AN ALT OF 6000 FT WAS GIVEN. I READ BACK LEAVING 11000 FT FOR 6000 FT. 15 MI LATER, ATC SAID WE SHOULD BE AT 8000 FT AND TOLD US TO CLB BACK TO 8000 FT. I KNOW I WAS CORRECT WITH THE CLRNC BECAUSE OF THE AGREEMENT WITH THE CAPT. ATC READ BACK, AND ALT SELECTOR SET AT 6000 FT. ATC MAY HAVE THOUGHT HE WAS WORKING ANOTHER SECTOR. HE COULD HAVE BEEN TIRED OR HE MAY HAVE BEEN LOADED UP WITH TOO MANY PLANES TO CTL.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.