This counts SCTP control chunks (like INIT, HEARTBEAT, SACK, SHUTDOWN - anything that isn't user data) transmitted by this device, explicitly excluding retransmissions, giving a clean baseline of protocol-overhead traffic. It's useful for capacity planning to separate genuine signaling overhead from the retried traffic that would inflate the picture, letting an engineer estimate how much of the SCTP traffic on a link is pure protocol maintenance versus actual application payload. A device with an unusually high ratio of control chunks to data chunks may be running with heartbeats configured too aggressively for the link's actual needs.