From reading through those pages and looking through the wiring diagrams, those 2 switches (min/max, 1/2) just adjust voltage, so you have 4 settings, by changing how many windings are used on the input side of the coil.
On page 6, it shows the 4 power settings, but not how they relate to the switches themselves (a.d. = power level 1, b.d. = power level 2, a.c. = 3, b.c = power level 4), via some experimentation, or an a/c ammeter (a clamp on one would be preferable), you could match the switches to which what they mean, and perhaps mark their meanings on the machine.
If you want to do a good job of welding, using the right settings makes a difference (both voltage settings, as well as wire speed). From reading it, the wire speed is adjusted automatically based on the switch positions, with the knob permitting fine-tuning of the speed.
Do some googling to read up on voltage settings and wire speed for mig welders, there's plenty of info out there, as it makes a big difference in the result you get...
And make sure you use flux-core wire...it's a lot more expensive than regular mig wire, but you aren't using shielding gas, so you have to use the flux-core stuff.