11. In this Part, in relation to residual disinfectant or a parameter specified in Table 4 of Schedule 3, and the supply of a volume of water within one of the ranges shown in column (3) of that Table, “the reduced number" and “the standard number" mean the number shown in column (4) and column (5), respectively, of that Table as applicable to residual disinfectant or the parameter in question by reference to a volume of water within that range.