|It is probably a scam.|
In the case of your registry there can be many orphan entries that cause no harm but will show up on a scan.
There is no need to pay for a registry cleaner and no reason, normally to even use one.
I suggest you remove the software and not worry about it.
If you want to try a safe and free cleaner download Ccleaner slim from the link below. The cleaner module is the forte of that suite but the registry cleaner has proven to be safe for me. For you own peace of mind when running either scan I recommend that you save a backup to the desktop when running. If nothing is wrong after a couple of days you can then easily delete the backup file. As I said, I have never had to use a backup file and rarely even bother with it.
Run the cleaner module regularly. You may need to re-login to sites like CN after using Ccleaner because it will remove that cookie. If you read the instructions you can set it to leave certain cookies.