Photone is a good App. A few people have done comparisons of photone vs other light meters and even against the gold standard Apogee sensors. It faired very well. So I would invest in the paid version of the app. I fully endorse data driven grows. The more data you have allows you to make accurate decision and the better your plants will grow.
If you also have an I-phone I recommend to also put the app on the phone. The reason behind this is to double check the readings. Sometimes phone manufacturers use different components from product to product and the light sensor on these tablets and phones are no different.
As to your lights. How are your plants growing? Do they seem to be responding well to your setup?
Anyone who is interested in the photone app.. Below is a really good review from the gentlemen who owns Migrow. His YouTube channel is a wealth of knowledge. I recommend anyone who is looking to learn about LED lights, proper color spectrums, PPF and Daily Light Integral, light color morphology in plants, please spend some time and go through his videos. It's a really good starting point.