B777 flight crew reported that fuel quantity on the totalizer and the FMC were not in agreement.

Attributes
ACN	1695774
Time
Date	201910
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZZ.Airport
State Reference	FO
Environment
Flight Conditions	IMC
Light	Night
Aircraft 1
Make Model Name	B777-300
Operating Under FAR Part	Part 121
Flight Phase	Final Approach
Route In Use	Vectors
Flight Plan	IFR
Component
Aircraft Component	Fuel Quantity-Pressure Indication
Person 1
Function	Pilot Not Flying First Officer Relief Pilot
Qualification	Flight Crew Instrument Flight Crew Air Transport Pilot (ATP) Flight Crew Multiengine
Experience	Flight Crew Last 90 Days 123 Flight Crew Total 2977. Flight Crew Type 234
Person 2
Function	Pilot Not Flying Captain
Qualification	Flight Crew Instrument Flight Crew Air Transport Pilot (ATP) Flight Crew Multiengine
Experience	Flight Crew Last 90 Days 149 Flight Crew Total 10295 Flight Crew Type 6361
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Procedural Published Material / Policy Inflight Event / Encounter Fuel Issue Inflight Event / Encounter Weather / Turbulence

Narrative:

During our arrival to ZZZZ; we were held and vectored off course for weather and a priority aircraft. After vector delays; we were cleared for approach. On approach and at about 2;500 feet; ATC issued a microburst alert of winds at +/- 40 KTS and shear of 800. After; the aircraft preceding us went missed approach and at about 1;900 feet; we went missed as we encountered the microburst and uncontrollable airspeed fluctuation. During vectors after the missed approach it was evident we would not be able to make another approach into ZZZZ; so we diverted to ZZZZ1.after several attempts to get a course or heading to our desired destination and evaluating our fuel; [we identified as an emergency] as our fuel on landing was indicating 4.1 on touchdown. After climbing and evaluating the situation; we determined that the fuel on board and the calculated fuel in the FMC were not in agreement so taking the safest course of action we changed our alternate to ZZZZ2 as it was closer and gave the FMC fuel on landing of 8.1. We landed and had 18.0 in the totalizer and 8.2 in the FMC.

Original NASA ASRS Text

Title: B777 flight crew reported that fuel quantity on the totalizer and the FMC were not in agreement.

Narrative: During our arrival to ZZZZ; we were held and vectored off course for weather and a priority aircraft. After vector delays; we were cleared for approach. On approach and at about 2;500 feet; ATC issued a microburst alert of winds at +/- 40 KTS and shear of 800. After; the aircraft preceding us went missed approach and at about 1;900 feet; we went missed as we encountered the microburst and uncontrollable airspeed fluctuation. During vectors after the missed approach it was evident we would not be able to make another approach into ZZZZ; so we diverted to ZZZZ1.After several attempts to get a course or heading to our desired destination and evaluating our fuel; [we identified as an emergency] as our fuel on landing was indicating 4.1 on touchdown. After climbing and evaluating the situation; we determined that the fuel on board and the calculated fuel in the FMC were not in agreement so taking the safest course of action we changed our alternate to ZZZZ2 as it was closer and gave the FMC fuel on landing of 8.1. We landed and had 18.0 in the totalizer and 8.2 in the FMC.

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.