just a reminder - values may differ from meter to meter if not calibrated. Uncalibrated Photone app gives me way lower values than ppfdmeter on my device with my lamps. So if you are in doubt and use photone, perhaps you are pressing too hard if you already are near the top values you read from your device.
If you don't calibrate, theres still some guessing.
I dont calibrate and couldnt find ppfdmeter in ios store so guess that is an Android app. Photone is known for not working as well with Android afaik. Going to download Photone on another iphone now and compare the results. New 2nd one to test has a film screen over the front camera so might have an effect. I had to take mine off to be sure but this will do for a comparison.