Azure Active Directory - trying to register custom domain name

Hello,

We are getting ready to migrate our exchange over to office 365. I'm getting AD sync prepped but to do that I need to register our public domain name.

WHen I go to Azure port, Azure AD, Custom Domains, it gives me the TXT record I need for our public DNS for it to register, I created it a few hours ago and I can check it using nslookup. However in the Azure portal verification I get this message When I click on verify. I've switched our domain name below with public domainname for privacy reasons.

This domain has been configured on (publicdomainname).onmicrosoft.com using Office 365. If you are the IT admin for your organization, you will need to remove or takeover the domain from the existing tenant before verifying
 it here.

This can be resolved using the internal or force domain takeover option.

Force domain takeover: If you are the IT admin of your organization and want to manage a single Azure AD with all users from Power BI or RMS to be migrated into this tenant, proceed with the force domain takeover option.

Internal takeover: If you wish to manage both directories in Azure AD and Office 365 to view users and their assigned Power BI and RMS subscriptions, proceed with the internal takeover option.

I honestly don't undestand the difference between force domain takeover and internal takeoveror if there is a way to find out why it thinks I need a takeover