@Doug-Robinson Each map calculates the route in its own way, and with its own errors. As example, one map could take into account a roadblock while another doesn't.
The same for GPS deives that use different maps and calculation algoritms. Hence it is normal that calculating a route with different maps gives different results.
As a golden rule: always calculate the routewith the same ap that your device is using: TomTom or HERE for Garmin.
When riding in a group with different devices, the mara routeplanner allows to compare routes so you can add/move waypoints until it is exactly the same for both device families
