For my situation, the 4g per gallon, in 170ppm tap water, was a little heavy.....In soil(ish) which is 50/50 FFOF/HF then cut 30% with plain perlite.....
Sometimes I have used as little as 1/4 tsp per gallon, which PPMd out to only 300(ish) , with my El Cheapo TDS pen, in which I have no idea whatsoever if it is anywhere near valid, in any way other that being relative to the base tap water reading....
I also immediately believed , that small scale weight measurement would give slightly inconsistent mix ratios, due to the physical structure of the dry mix....
All that being said, with the frequency I have to moisturize my smallish containers, a very slight variance in the nutrient dilution is understood to be negligible....
What is evident, is that my general "in the ballpark" mix ratios, are extremely precise.....