To delete the unwanted cameras, first disable the applicable cameras using the slider at the top left of each camera's title bar. Then click "show XX disabled cameras" below the display of cameras and you can use the trash can icons that appear in the title bar to delete them. In your screenshot you can see one such trash can visible on the camera that shows as "disabled".
The title of your message was "reset hub" ... It does not sound like you need to completely reset your hub, but in case you do, that's
hub settings > show advanced settings > reset
After resetting, you'd have to reactivate and set everything up from scratch.