In addition to the gpx files created in the sailgrib/track_aa directory, the track is saved in a database. The app uses the latter with a much faster access.
To delete old points from the displayed track , go to the menu and press the button. By default the last hour will be kept.
If you have subscribed to the Premium option, you can set the duration of the track to be displayed when the button is pressed: from 0 to 24 hours.