All incoming AIS information is taken into account in order to provide MarineTraffic users with the latest updates regarding vessel positions on the Live Map. However, a vessel can be out of range for various reasons - she sails on waters with insufficient terrestrial AIS coverage or mid-ocean where coastal AIS coverage is inadequate, for example.
The MarineTraffic System-related Events notifications let you know about such AIS-coverage occurrences the moment they happen. There are two available notifications of this type:
In Range: You get notified when your selected vessel re-appears within the range of MarineTraffic after having been out of range for more than 2 hours.
Out of Range: You get notified when MarineTraffic has no recorded data regarding your selected vessel's positions for more than 60 minutes.
The information you will be getting will let you know about the precise time (UTC) that such AIS-coverage events took place.