Does vehicle report odometer via ODB-II?

Just wondering if Bouncie reads the vehicle odometer via the ODB-II port or if it estimates elapsed mileage using GPS data?

The fact that an end user needs to input the initial mileage manually leads me to assume this value is estimated thereafter based on sensor data rather than the vehicle itself.

Though so far I have found it to be accurate.  I'm mainly just curious.

Thank you!