Diagnosis
The filter is exhausted but the electronic timer hasn't caught up. The light is on a fixed timer (or flow sensor estimate), but your actual water quality has deteriorated faster due to high initial TDS.
How to Fix It
Trust your TDS meter, not the light. Replace the filter now. The light is just a reminder; the meter measures actual performance. A reading consistently above 006 means the filter's ion-exchange resin is saturated.
If That Didn't Work
Ensure you're testing correctly. Test the water *after* it has passed through the filter—dispense some into a clean cup and then use the meter. Don't test water sitting in the reservoir, as it can mix with unfiltered water.
Heads Up
Filter life varies wildly based on your source water's TDS. If your tap water is very hard (high TDS), you may need to change filters long before the blue light turns off. The light is a guideline, not a guarantee of zero TDS.