Currently...
A - Reset at fill up.
B - What ever I want to monitor.
I think with B if you look at different trips, weather, speed, style, traffic, etc., you can get a firm grip on what your Insight like and doesn't.
I have set B and acheived 56.7 one way to work.
Then driving around my community, 48.4.
When you caculate TRUE, depends on what you are driving too.
Lots of "city" stop and go, short trips, not up to temp, etc, will chew it up.
Use the ECO Meter to help you acheive a good driving style.
Use the bar graph to tell you when you are in lean burn.
Setting B for some of these things will have you on your way