When your GPS is set to record Tracks it will continue to do this until tracking is turned back off, If your GPS is turned off after a trip and then turned back on in your house it will continue to record Tracks, some GPSs start a new Track if the power is turned off and then back on, while other GPSs continue adding new positions to the existing Track, I think your GPS is doing this last one, so it records your trip and then later on when you are at home it adds your home location to the end of the same track
The GPSs that don't start a new Track when turned on usually archive the current Track at midnight so you get a whole day saved every day, however you can force an archive at any time, so your options are :-
1) Force a Track archive at the end of a trip
2) Turn Tracking off at the end of a trip (and turn back on for a new trip)
3) Edit the Track with your 'line to home' to remove the 'Home' trackpoints