This is from the link on their site under PPS Pro:
"How do I start PPS-Pro?
We all know new setups are challenging. Plants need time to adapt to new conditions.
To begin, aquarium water can start at any nutrient levels. Then we start dosing daily PPS-Pro solution #1 (Macros) at 1 ml per 10 gallon or 40 L and PPS-Pro #2 (Trace elements) at 2 drops per 10 gallon or 40 L. (Daily dose of 1 ppm NO3, 0.1 ppm PO4, 1.33 ppm K, 0.1 ppm Mg, 0.01 ppm Fe(TE))
During this time and in to the future we need to switch from test kits to conductivity readings. This is easier, cheaper, faster and more accurate to overall living condition. Everything in an aquarium, alive or not, has some relationship to conductivity.
TDS-tester
The way it is done is to maintain consistent levels of pollutants, like fertilizers, substrate leaks, fish waste, decoration leaks and other with water changes. Some setups involve large water changes at times, and some more balanced, not so much. That’s the beauty. Plants and fish love consistency.
For example, when your tap is 300 µS, one PPS-Pro daily fertilizer dose is 6µS. This one dose is 1 ppm of NO3. So to limit the NO3 to theoretical 15 ppm we need to make sure the conductivity reading is kept under (6 x 15) + 300 = 390 µS with water changes.
If you feel like needing more fertilizer then there is no problem to dose more ml of the PPS-Pro solutions. The conductivity reading will take care of it and balance it out.
(1 ml = 20 drops)"
I guess because of the last sentence, I'm not going to worry about overdosing one time. Probably not an issue.