Ppm is parts per million or mg per liter.
You can add 40g in 100 liters (hectoliter) Fermaid O, or 40 000mg per 100 liters. Which (divided by 100) becomes 400mg per liter fermaid O.
This means that in a liter of water, the recommended dosage is 400ppm Fermaid O or 400mg.
From those 400ppm or 400mg, for the sake of the argument, 10% of fermaid's weight is assimilable nitrogen. 10% of 400mg (or ppm) is 40mg.
So with scottlab's reccommended dosage of 400ppm fermaid O, you will get (if only 10% of it becomes nitrogen) 40ppm YAN.
However, that link does not state how much assimilable nitrogen you will get, just the recommended dosage
You can add 40g in 100 liters (hectoliter) Fermaid O, or 40 000mg per 100 liters. Which (divided by 100) becomes 400mg per liter fermaid O.
This means that in a liter of water, the recommended dosage is 400ppm Fermaid O or 400mg.
From those 400ppm or 400mg, for the sake of the argument, 10% of fermaid's weight is assimilable nitrogen. 10% of 400mg (or ppm) is 40mg.
So with scottlab's reccommended dosage of 400ppm fermaid O, you will get (if only 10% of it becomes nitrogen) 40ppm YAN.
However, that link does not state how much assimilable nitrogen you will get, just the recommended dosage