We need to add something at the end of the chart indicating that some minimum level of Free Chlorine (FC) is needed even at the low CYA levels -- say, 2 ppm or so -- because some reserve needs to be available in case of localized usage from oxidizing organics or breakdown from the sun. Automatic dosing systems might be able to have lower levels, but manual dosing isn't frequent enough to maintain really low FC levels. So some common sense is needed. In practice, most people have 30 ppm CYA or more in the pool so the chart is fine in that area.
By the way, the basic rule that works pretty darn well (except for 0 ppm CYA) is that the Min FC is 7.5% of the CYA level, the Target FC is 11.5% of the CYA level, the Yellow/Mustard Min FC is 15% of the CYA level, the Shock FC is 40% of the CYA level, and the Yellow/Mustard Shock FC is 60% of the CYA level.
Richard