How the score is calculated
Each parameter is scored out of 100 based on how far it is from its ideal range, within range, top score; the further away, the lower the score. These are then combined with different weights, giving more importance to pH and free chlorine (the 2 that most affect the water's actual safety) than to parameters like calcium hardness, which affects the equipment more than the swimmer's health.
If free chlorine is at zero, the overall score can never go above a bare pass, without free chlorine there's no real protection against algae and bacteria, whatever the rest of the parameters read.
Combined chlorine is scored against the regulatory maximum (0.6 ppm). On top of that, if any value falls outside what RD 742/2013 requires of pools for collective use, the regulation applied in the Madrid region, the report flags it separately: pH 7.2 to 8.0, free chlorine 0.5 to 2.0 ppm, combined chlorine up to 0.6 ppm and cyanuric acid up to 75 ppm.