I do not know about all JD 3320s, but on my 2006 model. I insert the key into the switch (the key straight up and down), turn the key clockwise till you feel the bump, hear the fuel pump (I guess that is what that is) and solenoids, and see the dash lights come on. I allow the computer to do its self check of the systems (takes about three seconds). From that point you can either continue to turn the key clockwise until the starter engages and the unit starts, or you can press in on the key, the curly symbol on the dash lights, hold for 10 seconds or so and then turn the key clockwise till the starter engages and the tractor starts.
I know nothing about marks on the switch or five positions. Mine may have them but I use one to insert the key, two to turn on the electrics, and three to start the tractor. When I release the key it goes back to position two. All this is done mostly by feel, not by what the symbols say.
This is from the OM.....
A-Start Position - Turn the key to the start position to start the engine. Release the key after the engine has started and it will automatically return to the run position. The engine will continue to run.
B-Run Position - With the key in the run position, and the engine not running, the engine oil pressure light should flash and the battery charging light should illuminate. Both lights should turn off when the engine is running. You will also hear a clicking noise when the engine fuel shut-off solenoid engages. With the key in the run position, push the key in to activate the air intake heater system.
C-Off Position - With the key in the off position, all switched power is off, and the engine should not run.
IMPORTANT: Avoid damage! There is an accessory key switch position
(D) to the left of the key switch off position. Do not move the key switch
to this position. The battery could be drained.