B737-700 flight crew reported confusion with the final fuel numbers.

Attributes
ACN	1684725
Time
Date	201909
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Light	Daylight
Aircraft 1
Make Model Name	B737-700
Operating Under FAR Part	Part 121
Flight Phase	Parked
Flight Plan	IFR
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Instrument Flight Crew Multiengine
Experience	Flight Crew Last 90 Days 397 Flight Crew Type 19000
Person 2
Function	Pilot Not Flying First Officer
Qualification	Flight Crew Multiengine Flight Crew Air Transport Pilot (ATP) Flight Crew Instrument
Events
Anomaly	Deviation - Procedural Weight And Balance Deviation - Procedural Published Material / Policy

Narrative:

We received the weight and balance report at pushback. Our fuel gauges showed 18.8; but the wing tanks were only about 8.3 per side; with 2.2 in the center. I mentioned to the operations agent that it appeared they didn't completely fill the wing tanks; and she said that ZZZ is an 'over the wing' fueling station and it's because of the fuel density. I have no idea what an 'over the wing' fueling station means; but using 6.5 for fuel density puts us in the range (+/- 2%) of the gauges. No problem here. Now for the confusion.if you add the fuel; add up the fuel in (6;700 lbs.) plus the gallons added (1949 gallons at a fuel density of 6.5 equals 12;669 lbs.) the total is 19;369. However; the fob on the fuel summary shows 18;800. The numbers don't add up on the weight and balance report. The only way I can get 18.8 on the gauges with 6.7 inbound and 1949 gallons added is with a fuel density of 6.2.the simple math in the fuel summary block of the weight and balance report does not add up.

Original NASA ASRS Text

Title: B737-700 Flight Crew reported confusion with the final fuel numbers.

Narrative: We received the weight and balance report at pushback. Our fuel gauges showed 18.8; but the wing tanks were only about 8.3 per side; with 2.2 in the center. I mentioned to the Operations Agent that it appeared they didn't completely fill the wing tanks; and she said that ZZZ is an 'over the wing' fueling station and it's because of the fuel density. I have no idea what an 'over the wing' fueling station means; but using 6.5 for fuel density puts us in the range (+/- 2%) of the gauges. No problem here. Now for the confusion.If you add the fuel; add up the fuel in (6;700 lbs.) plus the gallons added (1949 gallons at a fuel density of 6.5 equals 12;669 lbs.) the total is 19;369. However; the FOB on the Fuel summary shows 18;800. The numbers don't add up on the Weight and Balance report. The only way I can get 18.8 on the gauges with 6.7 inbound and 1949 gallons added is with a fuel density of 6.2.The simple math in the fuel summary block of the Weight and Balance Report does not add up.

Data retrieved from NASA's ASRS site 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.