I’ll give this a try, but don’t want to make it overly complicated.
There is something called Daily Light Integral (DLI) which measures the amount of light your plant receives over a 24 hour period. The DLI requirements are highest during veg, but are easier to obtain because of more hours of light. When your lights are on 18 hours a day it’s easier to reach the desired DLI then when the lights are on only 12 hours a day.
There was a recent thread on DLI that had a graph showing the optimum DLI and how much light was required to meet those requirements.
The best investment you can make when using a natural light quantum board is a phone app that measures the amount of light your plants are receiving. I have an iPhone and used an app called Photone that measures PPFD or the amount of light per second. I compared it to a professional PAR meter and the phone app was very close.
If you get an app that measures PPFD you want seedlings grown between 200-300 PPFD, veg needs 400-700 with 18 hours of light, highest as approaching flower, and assuming 12 hours of light during flower, 600-800 PPFD in flower, the highest during mid flower. Fewer hours per day of light require even higher levels of PPFD. If you find the original thread there is a formula for calculating what is needed regardless of how many hours of light you give it.
With an inexpensive app you can eliminate all guessing.