Well done Retired F4
If my math is still worth a bit, than the GW over the period of time reduced from 1641:43 to 1706:43 by 11920 kg, while the TOTFW reduced only by 5400 kg?
The 777-200er (with TRENT 892) MTOW is 299,000 kg (660,000 lb), and it seems quite impossible that an ACARS message sent a GW = 492520 kg
"The Captain ordered 49,100 kg of fuel for the flight" (page 18).
So, GW is given in lb and FW in kg
and 11920 lb = 5400 kg