iPhone audiobook syncing issue: List not updating with imported audiobooks

I am having an issue with the syncing list not updating.

In the image below you can see a list of audiobooks from mp3 / CD import that are not on my hard drive (at least I don't think).

I have other books in my Books app that are not showing up on this list either.

I checked the iCloud and iCloud Drive and don't have any audiobooks on it.

I have all by music and audiobooks on an external thumb drive, though I learned, when I import a book into Books app it creates a copy of it on my Mac's internal HD.

Does anybody know how to get this to match up? Or where this list is populating is date?

I plug my iPhone into another Mac (eg: my work computer) and nothing is listed. This makes me think it is somehow connected my Mac laptop.

Any help is greatly appreciated!

[Re-Titled by Moderator]

Original Title: iPhone Audiobook Syncing Issue