what's the idea ppm?

I have a sativa dom. in potted soil outdoors in a 20 gallon'ish pot. What is the ideal fert. water ppm (I am using Advanced Nutrients Iguana Juice bloom 4-3-6). Also, what should I expect for runoff ppm? It's 300-310 steady for about 10 days. No signs of anything bad; nice,crystaly buds, just wondering what the high/low and ideal ppm is. Will ask the company also, however, I got the impression the last time I called them that not all of their phone personel have "field experience".