HUMA INLINE PCP REGULATOR

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I bought the Huma PCP inline regulator that screws into a DIN valve on a carbon fiber tank valve. The description of the regulator on the Airguns of Arizona says there are three settings, 1, 2 & 3. The regulator did not come with any instructions and there are no markings on the regulator that show a setting.

Does anyone know how to select settings ?