CT Clamp Calibration

I’ve purchase a couple CT clamps for playing around with and detecting whether some device are on. The one that I purchased already has the burden resistor and the clamp is calibrated for 20A → 1V. Question is do I still need to calibrate this manually, or just use the values for ‘calibrate_linear’ as specfied on the device like below?

sensor:
  # ct_clamp
  - platform: adc
    pin: ${adc_pin}
    id: adc_sensor
    update_interval: 5s
  - platform: ct_clamp
    id: ctclamp
    sensor: adc_sensor
    name: "Measured Current"
    update_interval: 5s
    filters:
      - calibrate_linear:
          - 0.000 -> 0
          - 1.000 -> 20.000
      - clamp:
          min_value: 0
          max_value: 20

I have done a calibration with a kill-a-watt meter but the values don’t come close to the linear mapping above. It was close to the kill-a-watt’s max of 15A, so this is why I question

Values from console mapping to values from the kill-a-watt:

          - 0.161 -> 8.45
          - 0.256 -> 14.40

Just following as I have some clamps that may need calibrating too.