At the end of the installation process after RegVac was installed, the checkbox that runs RegVac was checked. The installation program tried to run RegVac, but your version of Windows does not like the installation program running RegVac and so it gave you that error.
The installation was successful.
If you do not want to get that error, make sure the checkbox is unchecked.
The error message is saying that the program must be run "As Administrator" and it wasn't (this is what it means by "requires elevation." RegVac usually automatically runs "As Administrator," but when it is run by the installation program, that is not possible.
Like I said, the installation was successful. You will find that RegVac is installed and runs without that error (unless you do not have administrative privileges).