For soil, don't worry about it.
For hydro, just use the ratios on the bottles and the PPM should be OK. Start out with 1/4 strength, then gradually increase the dosage as the plants mature. For newly transplanted clonesb or seedlings, my PPMs with the Pure Blend Pro is around 600. By the time I get to the last week of the flowering cycle, the PPMs are around 1800. This will vary depending upon strain and the nutrients used. A lot is done by trial and error. Just be sure you don't burn the plants by using full strength too soon.
And, by the way ... there is no comparison between growing in soil and growing hydro when it comes to fast vegging. Plus, growing hydro takes all the guess work out of nutrient strength and watering schedules. Once you have it dialed in, its really very simple. Oh Yeah, and you don't have to worry about lugging all those bags of dirt, or where to dispose of it after harvest either.
Vi