B737-300 CREW HAD A FUEL GALLONS BOARDED; AND A FUEL QUANTITY DISCREPANCY. THE DISCREPANCY WAS NOT DETECTED UNTIL AIRBORNE.

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JUST PRIOR TO PUSHBACK; WE GOT THE LOAD SHEET FROM THE OPS AGENT AND I WENT TO WORK LOADING THE FINAL DATA INTO THE FMC AND OPC. THE CAPT ASKED FOR THE GALLONS ADDED AND AFTER CHKING THE LOAD SHEET; I RESPONDED; '1771 GALLONS.' THE FMC AND FUEL GAUGES SHOWED US WITH THE PROPER AND PLANNED FUEL LOAD OF '23.7.' THE CAPT THEN STATED THAT THE FUEL CHKED AND WE PROCEEDED WITH THE BEFORE PUSH CHKLIST. START; TAXI OUT AND TKOF WERE UNEVENTFUL. JUST AFTER TKOF; WE NOTICED THE #1 MAIN FUEL GAUGE READING WAS DROPPING QUICKLY. INITIALLY; WE THOUGHT WE MAY HAVE HAD A FUEL LEAK; BUT SOON REALIZED THE GAUGE WAS READING WRONG ON THE GND AND NOW SHOWED A 4000 LBS LOWER READING. BECAUSE WE WERE PLANNED TO TANKER FUEL; WE STILL HAD ENOUGH FUEL TO REACH ABQ; SO WE ELECTED TO CONTINUE. WE WERE ABLE TO XFEED THE FUEL BACK WITHIN LIMITS PRIOR TO OUR DSCNT INTO ABQ. THE PROB WAS A BAD FUEL GAUGE; BUT THE PROB WAS COMPOUNDED BECAUSE WE DIDN'T CATCH THE MALFUNCTION WHEN CHKING THE GALLONS ADDED. AFTER DISCUSSING WHAT HAPPENED; WE REALIZED OUR MISTAKE. WHEN THE CAPT CHKED THE GALLONS ADDED; HE HAD JUST SAID; 'THEY SHOULD HAVE ADDED SIXTEEN-NINE' (WHICH WAS CORRECT; 16900 LBS). BUT HE BELIEVES WHEN HE CHKED THE LOAD SHEET; HE INADVERTENTLY TRANSPOSED THE VALUE OF 'SIXTEEN-NINE' TO MEAN 1690 GALLONS. SINCE THE ACTUAL GALLONS ADDED WAS 1771 GALLONS; HE THOUGHT WE WERE FINE. IN FACT; WE WERE SHORTED ALMOST 4000 LBS. BOTTOM LINE: A SMALL MALFUNCTION AND A SMALL MENTAL ERROR HAD THE POTENTIAL TO ADD UP TO A LARGE PROB. SUPPLEMENTAL INFO FROM ACN 636655: JUST PRIOR TO PUSH; THE CREW EXPRESSED A DEGREE OF CONCERN ABOUT THE LARGE NUMBER OF 'MIDDLE EASTERN' MEN ABOARD THE FLT. WE AGAIN BRIEFED OUR PROCS. SIMULTANEOUSLY; WE DISCOVERED A COM PROB WITH THE PUSHBACK CREW. WE OPENED THE WINDOW AND SPOKE WITH OPS AGENT AND PUSH CREW AND OPTED TO USE HAND SIGNALS. I HAD JUST ASKED THE FO FOR THE GALLONS ADDED AS ALL THIS CONFUSION BEGAN. HE HAD ADVISED ME OF 1771 GALLONS ON THE LOAD SHEET. IN MY PREOCCUPATION WITH THE PUSHBACK PROCS AND THE PAX QUESTIONS; I TRANSPOSED THE 16900 LBS OF FUEL THAT I HAD PRE-COMPUTED WITH THE 1771 GALLONS VERSUS THE APPROPRIATE 2535 GALLONS I SHOULD HAVE BEEN LOOKING FOR. A SIGNIFICANT ERROR OCCURRED. UNFORTUNATELY; THE FUEL GAUGES INDICATED; IN ERROR; THE EXACT NUMBER OF FUEL WE WERE DISPATCHED WITH.