This information is republished from https://github.com/cardano-foundation/incentivized-testnet-stakepool-registry/wiki
One important thing to keep in mind is that the registry contains the registered metadata of individual pool owners (identified via their owner public key). A single owner may have multiple pools: Should several pools be registered on-chain under the same owner, the pools can show up in Daedalus with the same metadata.
Registering a new pool with an existing owner key doesn't automatically void the previous registration tied to that key. As a pool operator, you must explicitly retire pools that you want to have removed from the list. The creation of a retirement certificate is not yet supported by jcli but should be available soon. Please refer to the official repository regarding pool retirement: https://github.com/input-output-hk/jormungandr.