Some information regarding Hayward salt cells according to Hayward… the newer cells are being made with more rethenium plating on the grid than previously to extend the life of the cell. The added rethenium is causing the systems to read higher than previously, and it’s especially true of the newer TCell940, which initially gives a reading that is about 20% higher than the actual salt content. As the plating wears off (they stated about a year) the cell accuracy will improve . My guess is that whoever makes the grids for the Hayward cells also makes the grids for other brands, so I’d expect the higher inaccuracy to be the new “norm” for most, if not all cells.