It is possible that the underwing center wing tank fuel gauge could have read 300 pounds, which would be about fifty gallons. This is not an unusual discrepancy. In the first few days after the Flight 800 investigation Mundo asked a TWA official what exactly the fuel use log had shown in regards to the quantity of fuel in the center wing tank upon arriving in New York. This was an abnormality. He added that whatever level of fuel existed in the center wing tank at that time would not be entirely composed of fuel.
All fuel contains some water.
It's the same with the gas in your car. This combination of water and fuel is what the scavenger pumps transfer to the number two main tank. The amount drained is usually close to fifty gallons or around 300 pounds. In sum, the center wing tank of the plane that was about to become Flight 800 was empty or nearly empty before leaving New York in the late afternoon prior to its evening takeoff to Paris. Because of prevailing winds, planes usually carry more fuel when going west than when going east.