The speed shown in the application is the speed that was detected during the trip. This speed detection can suffer from interference which may impact its accuracy.
Examples of interference
The most common cause of speed interference is linked to GPS. Trips that encounter GPS signal issues may result in affected speed detections of your trips.
Your GPS signal may encounter issues if there are glass buildings, trees, tall buildings, tunnels, parking garages, etc.
All of these situations could block the GPS signal to the device. When this happens, the speed value could be skewed.