The device reports its location every 30 seconds, 1, 2, or 5 minutes while in motion. The reported speed is the speed when the location is taken so you will receive a speed alert if your driver is speeding at the instant of the location. The smaller the location interval the smaller the interval your driver can speed without detection. Similarly, with geofence alerts, the entry or exit of a geofence is determined when a location is taken. The smaller the time interval between locations means the sooner you will know when a driver has entered or exited a geofence.