Two different objects get mashed together in sales calls: copyright (the work) and ISBN (the edition identifier in retail systems). Confusing them is how authors sign bad deals.
Copyright
In the U.S., you generally own copyright in your original manuscript when you write it. A publisher only gets rights you grant in a contract. AuthorShelf’s public position: you keep 100% of rights. Read the Services Agreement before checkout anyway — that is the document that matters.
ISBN
An ISBN identifies a specific format/edition so stores and wholesalers can order it. Print and ebook typically need separate identifiers. Packages that include ISBN assignment remove a DIY setup step. Owning vs using an ISBN assigned in a production package is a metadata/retail question — it is not the same as handing over copyright.
Royalties
AuthorShelf does not take a percentage of book sales. Net to you is reported channel earnings minus print manufacturing cost for units sold. Details: How royalties work and the help article.