I have finished my first short novel of one hundred pages with approximately 55,000 words. I'd like to register it with the copyright office. I know I don't have to, that it's already copyrighted if it's fixed in a tangible form, which it is (hard copy, flash drive, and two external hard drives).

But I'd like to register it anyway. If I do, and I get a copyright number, what happens if I discover there are some grammatical or minor changes I need to make? Do I submit the revised copy and does it overwrite the original? Or do I need to copyright the revised copy? If the second scenario (copyright the revised), will I then have two copyrights?

I reside in the U.S.