Error 21916672: Variations Specifics and Item Specifics entered for a Multi-SKU item should be different.

This error indicates an issue with the naming or numbering system used for the variants (variations defined by Item.Variations.Variation.SKU) of a product listing. To avoid: check that variant names/numbers used are unique within the listing, check and comply with any platform-specific guidelines or rules regarding naming conventions, do not use restricted or special characters, and use a clear and simple numbering or naming system to distinguish each variant.