Yeah I've had some bad luck with light so i'm always going back and forth on it. I just need to read the plants from now onApp is ballpark start but this is precisely the reason it’s important to learn to read the plants response. Doesnt matter what number’s you have really because depending on genetics, environment, health and age of the plant, source of light etc ideal can drastically change.
Learning the signs is far far more accurate than any meter possibly could be.
With that said they can be a handy tool in replication from grow to grow and learning to read the plants responses