The playback limit, specified in the Advanced Settings tab of the Property Editor, permits one to limit the number of playing instances at any point in the hierarchy. If, for example, you set an actor-mixer's playback limit to "2", there will never be more than 2 playing instances per game object of any sound that exists under this actor-mixer.
However, playback limits follow the Wwise paradigm in that they can be overriden for specific children. When you override the playback limit somewhere in the hierarchy, you also define a play counter at this level. The following example will make this clear. Say you have an actor-mixer with 3 child sounds, A, B and C. If you set the actor-mixer's playback limit to "2", and you override sound A's playback limit and set it to "2", here's how playing instances are limited: at any given time, you cannot have more than 2 playing instances of B and C, and you cannot have more than 2 playing instances of A. Thus, you may actually have 4 playing instances under the actor-mixer (2 'A's and 2 'B's or 2 'C's, or 2 'A's and 1 'B' and 1 'C'), even though you set the limit to "2"!
In other words, playback limits apply to all sounds below the point where they are defined, except for subtrees for which playback limit was overriden.
The same considerations apply to the interactive music hierarchy, and to the master-mixer hierarchy.
