On second thought, there must be a point where it is adding trips together and where it doesn't, and resets.
For example, I'll drive 12 miles in the morning. When I stop at work, it reports this. 8 hours later, when I drive home, it will report a fresh 11 or 12 miles ... not 20+ as if it added the morning drive in.
If I drive the vehicle later that evening, say an hour or two after I get home, I'll see something like 16 or 17 miles and that WOULD seem to be adding in my previous most recent drive. Hmm.
You would think this little "drive summary" would simply reset every time the vehicle is parked and turned off.