New to the SGII
 

I received my SGII a few hours ago. I plugged her in and set my tank size and all of my units of measurements. That is pretty much all I have done. What are some of the other things I need to do? Adjust the speed with a GPS? Set the Cuttoff?

When driving I saw my MPG read 9999. Why did it do this and what is the best way to fix it? My engine is still running when I coast. Also my jeep has a 13.6 gallon tank. Should I set the tank size to 13 or 14?

Thanks for the help.

9999 mpg is seen when you let go of the throttle while in gear , and the engine goes into DFCO - decelleration fuel cut off.
No fuel is being used as the flow is cut off, but you're still covering distance.
In Maths you should get a division by 0 error ;)

Set the cut off, and start calibrating the SG when you fill up (menu item FILLUP).
Compare the SG's estimate of the fuel used, with the actual volume you tanked.
Correct the SC using the < > buttons, but only correct it halfway towards the actual value - otherwise it may swing the other way on the next fill up.
The correction will quickly get smaller over a few tanks, and the readouts will get rather accurate.