Don't know why they tell you that. Maybe it's poor training of sales ppl. by a local feed rep. I've read several scientific studies that were suggested by members here. They all suggest that growing chicks can be harmed by too much calcium. They also all suggested that you start feeding layer feed when you see the first egg. It may not noticably affect the chicken but it may not be as healthy as possible. Don't throw the layer away, just keep it sealed and dry until it's needed. Please understand that ppl here aren't trying to be critical but wanting you to have the best info. possible. Good Luck