Grave Walker Witch Question

[CardenBekes]

S i have a question about the witch grave walker class archetype, in the beginning of the description :
Unlike the creations of standard necromancers, a grave-walker's creations remain forever tied to her will.
does this mean her graveyard bucket doesn't overflow ? or what?

[Decimus Drake]

When she takes control of an unintelligent undead with her bonethrall ability the duration is permanent and is even maintained when the undead leaves her aura. She can control 1 HD of undead per level in this way. I'd say that if she tried to control more then her limit the ability simply wouldn't work on the would be new recruits.