Migrating multiple Photos libraries into Lightroom CC

Hi all,

I initially tested the process of moving pictures from Apple  Photos to Photoshop Lightroom CC with a small library that I created. The process went fairly smoothly so I wanted to continue moving photos over in separate, smaller libraries, rather than the entire thing. Apparently that's not possible:

I'm getting the error below:

Error: Already migrated. You already moved this Photos Library to Lightroom CC.

Solution: A Photos Library can be migrated to Lightroom CC only once. You can, however, migrate additional libraries.

My questions are:

1) I didn't already migrate this particular library to LR. This is a library with a different name and different photos.

2) In the "solution" section above, it says that I can "migrate additional libraries." How does one do that?

Thanks,

Jeff