The starter is for making working solution out of developer replenisher only. It is not for use with ordinary developer. It primarily supplies the halide restrainer the developer needs that the replenisher lacks, as it is not needed for replenishment since the halide is produced as a by-product of development. Therefore if you make a working solution out of replenisher you must add the starter (halide). Ordinary developer mix and used developer already contains the halide.