This means if your user is assigned a Deskphone (ie. Polycom or Cisco physical phone) then you can log into one PC using the RingCentral for Desktop app and this will be your additional softphone.
If your user is assigned the RingCentral for Desktop phone, and you log into the app on one PC, then you still have not used your additional softphone, and you will be able to log in on another PC without having to de-authorize the first one.
Brandon makes a good suggestion, you can log into the RingCentral for Google extension on the Google Chrome browser, and this does not count as an additional softphone, so you can still log into the RingCentral for Desktop app on a separate PC, you do not have to de-authorize the RingCentral for Google extension.
If you need or prefer to use the native RingCentral for Desktop app, you can have your administrator add an additional RingCentral for Desktop device to your user. However, this increases the price you would pay for your service.
I hope that makes sense and helps clarify things a bit.
I agree with your comments and for most users this would be fine, however I'm guessing there are a few users like Mike and I who go back and forth between a laptop and a desktop and would like to use the RingCentral Desktop app when we are using either device. I understand that having two softphones active at the same time to send calls could be problematic. Just curious if for situations like ours there could be a toggle built into the softphone that allows it to activate and use the current device that we are logged into; e.g. if logged into our desktop then that would be the current active softphone, if logged into our laptop then that would be the current active softphone. The task of logging into the web interface to deactivate and reactivate is annoying and it seems there should be an easier way to tackle this issue.