The phrase "single copy" refers to having only one version or instance of something. It means there is just one of it and not multiple copies or duplicates. Full definition
Authors, particularly self - published authors, often go to great lengths to promote the sale of single copies of their books. (blog.publishedandprofitable.com)
Besides, I don't think publishers are going to stop selling single copies of games any time soon. (n4g.com)
But back then it was all about home delivery and single copy sales of the print newspaper. (talkingnewmedia.com)