Question about readings

I have been using a Vivosun TDS & EC (hold) meter and I’m not sure how to read it. Before watering with straight purified water my EC was 27 and my PPM was 6. Taking a sample of the runoff my EC was 345 and my PPM was 175.
Checking the FF watering guide, they recommend an EC of 1.70-1.90 and a PPM off 1190-1330. (Just an example of how they have it for week 5).
I have no idea how to convert my readings to their readings. Do I have a faulty meter or am I missing a step or two?

Your meter reads in micro Siemens and you’re looking for milli Siemens. You need to move the decimal place 3 places to the left on your ec. So if you’re a reading of 345, it’s actually .345 ec


500 ppm NACL scale equals 1 EC.

Like @BobbyDigital said; you need to move decimal to the left.