This record should point your AD FS namespace (for example, fs.contoso.com) to the internal IP address of your AD FS server ...

This record should point your AD FS namespace (for example, fs.contoso.com) to the internal IP address of your AD FS server farm, which may be a load balanced address. You can use the ping command to test that the record resolves correctly. If your organization has multiple offices, try pinging your AD FS namespace from a computer in each office to ensure the record has replicated to all DNS servers.