The FMCSA requires that an ELD read the engine odometer, which is separate from the dashboard odometer.
The ELD mandate is very specific about how ELDs should get the odometer reading for e-logs. The engine odometer is based on engine shaft rotations, and is more accurate than a dashboard odometer, which is based on wheel shaft rotations that are affected by changes in tire size and pressure.
For most vehicles there will only be a small difference between the engine odometer and dashboard odometer values. If the vehicle has had extensive engine work done such as a rebuild, then the engine odometer can be reset to zero and that difference from the dash odometer can be pretty large.
The most important thing is that your BIT ELD is reading the engine odometer and adding it to your logs for you automatically.