ScanGauge II fillup reset do it or not (for relative MPG tracking)?

[2009Prius]

I have been diligently recording the average trip MPG and other trip parameters reported by ScanGauge II at the end of each trip. I never reset the MFD MPG - I want to use it as a lifetime MPG estimator (in addition to calculating total miles divided by total fuel pumped). So I use the ScanGauge trip MPG to give me feedback on fuel economy for each trip.

At each fillup the ScanGauge II has been quite accurate in determining the fuel used so I didn't have to change the amount of fuel added - until the last tank, ScanGauge thought I used 8 gal. but I could only pump in 7.8 gal (this was after the auto shut off, I pumped again and soon afterward it auto shut off again. In the past I never pumped again after auto shut off). This maybe the first encounter of the notorious bladder problem for me.

My question is how does the ScanGauge II calibrates itself with the fillup data. Does it remember all the previous fillup data or just the last fillup? In the former case I think it is better to enter the fillup data and the noise introduced by the bladder problem will be averaged out, but in the latter case it may be better not to enter the fillup data so that we can avoid the noise introduced by the bladder problem (and pump variation for that matter).

[fjpod]

I believe you can calibrate it once and it should remain accurate in regards to the amount of gas taken in a fill-up. I check mine sometimes and find it off .2 or .3 gals. sometimes. I usually re-calibrate it.