B737 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Flight Crew Type 207
Situational Awareness
Deviation - Altitude Crossing Restriction Not Met; Deviation - Altitude Undershoot; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued New Clearance; Flight Crew Requested ATC Assistance / Clarification
Human Factors; Procedure
While descending on the WINNG 1 RNAV arrival into ATL; ATC issued us a clearance to cross ERRGO intersection at 12;000.  Upon receiving the clearance; I as the PM; set 12;000 into the MCP window.  Both the captain; who was the PF; and I verified the set altitude and verified the restriction programmed in the FMS.  What we failed to notice; however; was that it was not a hard altitude of 12;000 programmed; rather 12000A.  It was set like this because that is the published restriction on the WINNG 1 RNAV arrival.  Both of us discussed the NOTAM to disregard speeds and altitudes on the arrival; but decided rather than go through the arrival and delete all of these; we would leave them in place for descent guidance only and delete them later; as instructed by ATC. Although we identified this threat at the gate; we still failed to trap the erroneous altitude restriction and correct it later when descending into ATL.  Once the aircraft had been in a descent for a short period of time; the PF recognized that the aircraft would be high at the waypoint and almost immediately thereafter saw the error in the FMS.  Using the speed brake to assist in the descent; we also requested relief on the altitude from ATC.  The approach controller to whom we were talking coordinated with the center and gave us relief; by means of a descend and maintain clearance (9;000) just prior to waypoint passage.
I believe that I did not monitor the descent path well enough and should have picked up the vertical deviation earlier; if not my FMC programming error as well. I think that some level of fatigue from two consecutive poor nights of sleep may have contributed. I just did not sleep well in the layover hotels; no particular reason except perhaps having had too much 'fatigue countermeasure' (coffee) during the preceding flying days.
B737 flight crew reported missing a crossing restriction of 12;000 feet due to the restriction having been previously programed by the arrival as 12000A.