Not recognizing correct Author

Hello. I’m pretty comfortable using WP. I recently started a blog where I am using different authors for the first time. However, if i am logged on as ADMIN, WP will not show that the posts are created by ADMIN. Instead, it chooses the top author (listed alphabetically.. in this case the author is named ‘cb3d’). I thought I could possibly change this using the ‘Post Author’ Box on the bottom right of the ‘Write’ page, but ADMIN does not show up as an option there either.

An old post still shows up as ADMIN, but that was before i added my AUTHORS. Is this a bug, or am i doing something really stupid? Or is it expected that I create another AUTHOR name for my posts? (the site is 3dmeca.com)

Thank you for any help in this regard.