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No, these bulbs don't have twice the amount of xenon pumped into them. It is simply an analogue of the double H4 halogen used in the combined headlight of the high beam and dipped beam. Since it is impossible to make two discharging gaps, the lamp socket has a mechanism (solenoid or electric motor) which moves it back and forth a few millimeters. This is how you get the desired light distribution in each mode.