Just to add that negative Longitude readings = West, positive = East.
Your True South position is based on your Longitude position, which is why you have everything set at 0, when starting, then, if using USALS, you enter your Latitude, and Longitude, into your receiver then drive your motor to a suitable satellite, for alignment, preferably one near to your true South.
Once done you physically move your dish/motor, on the pole, until you get the strongest signal, from your selected satellite.
Once done you tighten eveything up, carefully, so that it doesn't move, then use your receiver to send it to your furthest, available, East satellite, usually 39E, then furthest, available, West satellite, usually 30W. Make a note of the signal quality readings, then send it back to the initial satellite, you used for alignment, to make fine adjustment, to get it tracking the satellite arc correctly.