The light sensor on the DrDAQ is a photodiode, it has no colour filter or focusing lens.
You will find graphs of 'Typical Photodiode Spectral Response Curves' on the internet.
As it has no focusing lens, over the area of the photodiode, this makes hard to calibrate the sensors intensity.
The light intensity measurements are radiometer.
You may find fitted your own lens and then comparing this to a calibrated light meter, may give better result which you could use to calibrate the level.