Generally we refer to "unfiltered dispatching" when no limits on the frequency of updates is applied to an Item.

As well as the snapshot settings, the frequency settings can be configured both server-side and client-side.
On the server side, by the function getAllowedMaxItemFrequency, you can set an upper limit on the frequency for each Item.
On the clients side, by the function setRequestedMaxFrequency, you can choose for each of them its proper frequency limit, even dynamically during the life of the subscription.

Please refer of section "3.3 The itemEventBuffer" of "General Concepts.pdf" document for further details.