Calling EC and TDS the exact same thing is a massive disservice to growers. They represent fundamentally different principles, and understanding the nuance between them is the key to managing root-zone health. EC is the driver of osmosis; it's not just some metric made up just so cannabis cultivators can measure their cannabis nutrients "feed". To tell growers openly that ec is the same as tds is lazy. Purely synthetic delivery, tds will never be higher than ec unless there is alot of organic matter present. TDS is almost universally lower than or equal to EC when read in equivalent units. So whether tds is higher or not depends on what your feeding her and indicates how much shit is organic comparable to salts in ionic form (ready for uptake).
Inflow(Feed) EC: 1.2mS/cm to 1.5mS/cm. (600 ppm to 750 ppm)
Root Zone EC: 0.8mS/cm to 1.1mS/cm. (400 ppm to 550 ppm)
Runoff EC: Slightly lower than your inflow EC. If your runoff EC is significantly higher, salts are building up; if it's lower, your plants are hungry.