A TDS meter does not measure contaminants. It will not tell you if your water is healthy. The TDS meter reading simply refers to the amount of total dissolved solids in your water, it will not tell you what those solids actually are and if they are harmful for your health.
For example, you could have a high TDS meter reading but no harmful contaminants in your water. Some healthy minerals like potassium, magnesium, and calcium can actually cause your TDS meter to spike. So, any water filter with a remineralizer could cause a high reading on your TDS meter, even though the remineralizer is adding good minerals that you want.
On the other hand, you could have a low TDS level even if several harmful contaminants are present in your drinking water. Your water could have heavy metals like lead, or other contaminants like pesticides, pharmaceuticals, or hexavalent chromium. The TDS meter will not pick these contaminants up.
This is why you shouldn’t rely on a TDS meter to determine your water quality. You need to understand not just how many dissolved solids are in your water, but what those solids are and if they’re harmful for your health.