4 headlight system, inner headlights are dual filament, just like a 2 headlight system, and they operate the same way. The outer 2 headlights are high beam only, so...
Dimmer switch on low, you get the low beam filament on the inner 2 headlights.
Dimmer switch on high, low beam filaments shut off, high beam filaments on the inner headlights come on, as well as the outer 2 (high beam only filament)
