Forum:Iron core of koa'ki mieru

i've been needing to know the answer to this question, and are hoping someone can offer the correct ruling, when using the discard of an iron core to keep a koa'ki meiru monster on the field, can you dump only one iron core to keep multiple monsters? i ask this because says you must discard "an" iron core, and i am dumping one, so does dumping the one apply to others?