Installer still present
Once ProofBuddy has been successfully installed you can remove the /admin/install/ folder from your server. Leaving this folder on your server after an installation may present a security risk, plus deleting it will free up a little space.
How do I remove the /admin/install/ folder from my server??
In the /admin/ folder under where you uploaded ProofBuddy is a folder named install. Once you have ProofBuddy up and running you can safely delete the /install/ folder and you won't see the message anymore.