[quote=@Fabulous Knight]
[@Kho]How are they using a domain before level 7?
[/quote]

It's a game mechanic. You can see it as: you get to add a new domain at Level 14 and then every 7 levels after.
Or you can see it as: every 7 levels sustains a new Domain, and your initial Domain becomes sustainable at Level 7 (though usable before).