Hello, John.
The real-time module needs to be the same version as your version of CVI. If you have CVI 8.1, you can only use CVI RT 8.1. It looks like you are trying to install CVI RT 8.0 with CVI 8.1, and that will not work.
Looking at your screenshot, I agree that the message you got was misleading, since it says "minimum". I believe that the reason for the misleading wording was because for CVI RT 8.0, the CVI environment could not be 8.0. It had to 8.0.1, or later (meaning 8.0.2, 8.0.3, etc...). That's why it said "minimum". But after 8.0, "minimum" was removed.
Luis