The hosted domains feature of a hosting account refers to the amount of registered domain names that you could include in the very same account. Registering a domain and hosting it are 2 completely different services although many people consider them to be the exact same thing. While the registration means you become the owner of a given domain, the hosting aspect is what actually permits you to have a website because this is where your files and e-mails will be. Since these are 2 separate services, you'll be able to register a new domain with one company and host it with another one by modifying its name servers (DNS) - the domain name is going to work in the exact same way as if it was registered and hosted with the same company. It's also extremely important to know that changing the hosting means pointing the domain to an alternative company and not transferring it.