A330-FDR (unclear GWC value)

[ex902]

Hi,
I study on a set of FDR about A330 on medium and long range flights. However, may be because there was a systematic mistake, the gwc (supposed to be aircraft mass in tonne) column shows value as if they are percentages (I come to this conclusion because the top value of all values are less than 100.0) but not absoulte tonne. For instance, there are some examples as follows:

• values start with 3.52 during takeoff, decreases first, and then suddenly changes to 99.83 when the aircraft reaches at 28000 ft and regularly decrease during cruise.
• at takeoff gwc is 88.17, at TOC it is 83.3 and regularly decreases to 59.14, after 5 hours flight with 24 tonne fuel burn. So 24 tonne fuel burn accounts 29.03 decrease (88.17-59.14) in gwc.
• at TOC gwc is 98.76, at TOD gwc is 70.7, the fuel burn during cruise is 28.2 tonne.

I made some calculations and as a result I was wandering could this percentages show relative change in 'fuel on board + payload'? Is there a such common sense of aircraft mass using in FDR?

I studied lots of FDR of many aircraft type and I have never seen a case like that. So if you have any idea what that would be, I would greatly appreciate.

Excuse me for long message.

Regards