Torque other ODBII scanner setup

Have the TORQUE odb2 scanner android program hooked bluetooth to my KIWI plx dealy.

I get various results. Throttle seems to go from 17%-87% Coolant temp gets to 185 and the IA temp sits at atmospheric till it gets hot. But it initially matches the temp on the head liner when I get in so I think it's accurate.

Anyone know of any particular setup these things need to get em working right?

One thing that is far off however is the MPG calculation. Anyone know how it goes about figuring MPG? I put in something like 1900kg for the truck's weight, think it says that matters in a 2 second blurb that flashes when I turn it on.
Thing is, according to the mpg calculator I get roughly 25mpg per trip. But when I actually fill the thing. 18 something per gallon every time.
the program seems to be solid precise just not accurate. Needs some tweaking. Any help?

I've got a 2010 4 litre 6 speed 4x4.