Servos are basically just small motors with a potentiometer and a small control circuit. The potentiometer info is processed to determine the current position of the motor, and its position is adjusted based upon user input. The programming input that we send to the servo is generic and could have been anything. The choice to use 360 degrees seems like an odd choice to me, but it works.
What you are actually doing is sending a signal to the control circuit inside the servo and telling it to turn the motor as needed until the potentiometer reads a precise value. The lowest reading that the pot can read will generally be the farthest counter clockwise rotation of the servo. The highest reading of the pot will be the max rotation clockwise.
Because your signal is actually telling the servo to adjust the location of the pot, the max and min position of the servo shaft is dependent upon the gear ratio that connects the motor shaft to the pot.
That means that the min/max rotation of a servo can be almost anything. When you input the code for 360, you are just telling it to adjust the internal potentiometer to its max setting.