If you understand the equation for DLI, then you can easily extrapolate all you need to know. Turns out learning and understanding math is incredibly useful in life :P You don't need to be an expert to understand 1 small slice of physics/chemistry. Some founddational knowledge does help, though.
whether autoflower or photoperiod, the numerous local variables makes this a matter of some trial and error no matter what. Observe and react. This stuff is merely a tool to shorten that learning curve.. less trial and error to get to the same ending point. LEss wasted time and effort figuring things out.