How to calibrate Dome Multiplier

I search a lot and find all light meter code are using the same santance

" DomeMultiplier = 2.17 (calibration) "

My question is, how do you calibrate the sensor with a white dome?

Which lines to edit (if any)

I was referring to BH1750FVI with a white dome.

Your post was MOVED to its current location as it is more suitable.

Could you also take a few moments to Learn How To Use The Forum.

Other general help and troubleshooting advice can be found here.
It will help you get the best out of the forum in the future.

Thanks

To calibrate that light sensor, you will need either a calibrated illumination environment, or a calibrated light meter to compare readings.

Yes, buy what is to calibrate? I mean what to write in my sketch?

To "calibrate" in your case means to find a number to multiply the readings produced by your light meter, so that they agree with the readings produced by a professional quality light meter, under the same lighting conditions.

Calibration tutorial: Why Calibrate? | Calibrating Sensors | Adafruit Learning System