What’s the tag added when adding terms from Rankings Discovery?

To help you easily identify the terms added to each URL from Rankings Discovery, once added, they will be tagged with "Discovered-[number]".

When adding at the same time, discovered terms for a few URLs, terms added to each URL will be tagged in a separate tag.

You can rename the tag later, or you can delete it if you want to. From the left menu:  URLs & Terms > Term Tags.