This is on PC.
I've included two screenshots here.
#1, notice the Block is 84.5, the FOB is 37.3, the Trip is 23.2, the DEST is 14.1, and the EXTRA is 48.
Block-FOB is 84.5-37.3=47.2, which is just about 48.
The DEST fuel is correct. Simbrief estimated me at about 13.5 at landing.
I have no idea where it's getting the TRIP of 23.2. Should be 70.4. Obviously it knows that, since BLOCK-DEST=70.4.
The second screenshot I've loaded more fuel, FOB is 37.5. BLOCK-FOB is now 47.0. EXTRA has decreased by .3. Trip has gone up by .2 (!?).