The way that content sorting works is the category does not matter too much. It's mainly used by curators to pull a list of posts, but that is infrequent.
Tags, as you probably noticed, work like this: the first tag is the category and is permanent. The subsequent tags are ordinary tags and can be changed. In your case, all you had to do was edit the subsequent tags. Double-posting doesn't do any favors for your profile and is best avoided where possible.
Thanks, will take care of this in future.