Metering calibration allows to match level readouts from the Bettermaker unit with values in your DAW and/or audio interface. It does not affect audio levels within the unit (for example it doesn't make Mastering Limiter output level higher), it only affects level meter values. The calibration process is quite easy, simply connect the unit directly to your AD/DA converter and play sine tone from your DAW. Observe input and output levels in your DAW (or audio interface). Open calibration screen in your Bettermaker unit and follow on screen instructions to match the readouts with DAW.