If you have two bulbs on each side,

The high beam is served by two bulbs .
Low beam is served by one bulb


The low beam is run by the bulb with two powers, three contacts, 2 filaments .. the low beam filament is shrouded, the high beam is not.



H4 55W/60W for low beam and half of high beam

H1 55W for the other half of high beam