1.2.1 seems to have introduced a bug on the Fuel/Load page. After inputting ZFW, ZFWCG, and Block fuel, the fuel prediction to dest appears. This part works as it always has. But it shows a massive "Extra" value at the bottom of the page. In 1.2.0, this value worked as it should - it was (Trip Fuel - Block Fuel). So if your Block was 50 and your Trip was 38, Extra was 12.
Now, Extra appears to show the difference between the Block fuel and the currently loaded fuel (Block Fuel - Loaded Fuel). So if my Block fuel is 50 but I've only loaded 15, Extra shows 35.
If you refuel the plane progressively, you can watch the Extra value slowly move towards the correct value.
Very odd.