JCJP,
Thank you for the inquiry.
For TZTL12F;
Home---Settings---Units---Position Format---Loran C---<
Loran C Station & GRI--- (select proper GRI area for your location)---- Slave 1---(select proper slave for your area)----Slave 2 ---(select proper slave for your area)
It is also possible to enter a manual correction to each X & Y coordinates.