The Time Position display on the Transport bar usually starts at “zero”, even if the incoming time code is something else. But if you want Song Position 1.1.1.0 to correspond to some certain Time position on the Transport bar, set this value with Time Display.
This value will be used for the time position of the beginning of the song.
If you for instance want the Transport bar to show the actual incoming time code values during external synchronization, the “Song Start” and “Time Display” should be set to the same value.