I've seen others make the same mistake here on AFN - presuming that their variable intensity grow lights have a linear 0-100% adjustable scale, while for ex., the HLG-300L rspect quantum board dial adjusts with 10 clicks/settings from 60-270 watts. Thus, 5 out of 10 clicks/settings is not 1/2 power.
HLG and other lights with variable dials should disclose the actual light intensities for their dial settings! Or even more of us need to use a cell phone, lux meter or other methods of estimating light intensity.
Growers who make decisions based on such such assumptions about light intensity settings could be setting themselves up for major problems, including over-dosing seedlings; wrong calculations of yield/watt, etc. For ex., they may assume a 2 out of 10 setting is 20% power while the HLG scale actually starts at 22% power, and at setting 2 the plants would apparently be getting ≥100 watts or ≥37% power, over 50% more than expected. And another problem is that unless disclosed by the manufacturer, we don't really know that the dial settings are linear, an equal amount between each setting.