If you are viewing the Outbound Communication Status area in Core iQ, there may be a grey button in the top right hand corner that says Clear # Unprocessed. This button is used to completely clear the cache of items for that campaign which have not been processed by Core iQ. This number is a rollup of all the items that have a status of: New, Past Due, Pending Admin Approval, Removed by System, Rejected by Admin, or Failed Processing. If you click the Clear # Unprocessed button, any items that have a status listed above will be move to a status of Removed. This means that these communications will be placed in an area of Core iQ where they cannot be processed. Use this feature whenever you want to bulk Remove items that you have no intention of allowing to leave Core iQ.
Please note that in v2.1 of Core iQ and later, Core iQ no longer counts Removed by System items in the 'Clear # Unprocessed' button