Ideal DLI values ?

Dr Bruce Bugbee's videos are a great source anything regarding PPFD, DLI, wavelength, etc. There's even a reddit AMA he took part in. Info gold.

I think those numbers are crap personally.. but go for it and see how it works. You shouldn’t be cutting DLI in half when starting 12/12 IMO.

FMO, nothing more nothing less. It will not make diddly squat difference to the average home grow. They just want your money. Better to concentrate on getting your feeding and watering right, this will affect your outcomes more than any photone app. Focus on what you have, not on what you might have. If you had a five acre indoor grow and were trying to minimise costs and maximise profits then these things would be useful, but for the average person growing at home with an average light, things like this are just designed to make your money, their money.

"max" dli depends on numerous relativistic numbers... does the app ask for area of coverage? if not i find it hard to beleive it is calculating DLI accurately. temp, rh% and ambient co2 will all impact how much a plant can handle. these devices can still be useful. They inform about relative intensity under any 1 light... i'd be wary of comparing results between any 2 lights with different properties/characteristics. So, you'll be relying on observing and reacting to plant... the measurement you take whether photone or lux will give a realtive intensity "mark" to follow in future under that light... any significantly different spectrum and you need to step through that process again. important to measure in same exact spot and same exact distance... use a string or something similar and makr where it hangs fro for the measurement to be consistent... the rest of the coverage will be proportionally the same as before. even with a real per meter, you still need to go through that trial and error with the plant to see how far you can push it.... your ambient environment will flcutuate if not tightly controlled, so be ready to back off or amp up over time as it will not always be the same. Either case, these measurements will get you within a small distance fro optimal, but still have to react to the plant. the more tightly you control the environment and teh better the equipment (a real par meter in this instance) the smaller the ballpark you start in... imho, don't spend hundreds on a real par meter, but also don't get sucked into an obvious llie... if it is free, use it like a lux meter, otherwise i'd buy a cheap lux meter. the sensor is better for a more true directional reading. phone lux meteres almost always exagerrate the value because your camera lense isn't made to do this well.