I notice that Myles' gauges also show the  weight on the gauges as KG, mine remain in LB. That's because I'm using the US System (feet,inches), and not Metric, or Hybrid.

I did a test by changing the settings to Metric, and there is definitely a bug. Max fuel in Wing Tanks is 2066 KGS, with 3188 KGS (a total of 7320 KGS, instead of a total of 161xx KGS (CDU only show a maximum of 16.1 tonnes)) for the centre tank! The same happens when I change to Hybrid.

There is definitely a bug with the Metric fuel quantities.