The KeyFrameCount with DataType UInt32 is the multiplier of the PublishingInterval that defines the maximum number of times the PublishingInterval expires before a key frame message with values for all published Variables is sent. The delta frame DataSetMessages contains just the changed values. If no changes exist, the delta frame DataSetMessage shall not be sent. If the KeyFrameCount is set to 1, every message contains a key frame.
For PublishedDataSets like PublishedDataItems that provide cyclic updates of the DataSet, the value shall be greater or equal to 1. For non-cyclic PublishedDataSets, like PublishedEvents, that provide event based DataSets, the value shall be 0.