If you open it in PKHeX, it will show you all the details for ball and stats. Use the encounter database when generating Pokemon, as the program will set everything up for you from the template.
When eggs are created, the game sets the nickname field to that of the species' name, then it sets it to "Egg". Due to how the game overwrites strings, it does not clear the unused characters that are reserved, so the longer name (in this case, Oshawott) is not entirely overwritten by the new name (Egg). The leftover unused characters are called "trash bytes", and since your file dies not match the leftover values expected in this situation, it is flagged by the legality checker.
The trash byte viewer/editor is accessible by control-clicking the text box responsible for the name you would like to inspect.