This counts EIGRP Conditional-Receive packets sent on the interface -- special packets used as part of the multicast flow-control sequence to tell peers to hold off processing further multicast until told otherwise. Because CR packets only appear when EIGRP's flow control kicks in to protect a slow multicast receiver, any non-trivial count here is itself evidence that at least one neighbor on this segment has been struggling to keep pace. An interface that has sent zero CR packets for months suddenly logging a burst of them coincides with, and helps confirm, a slow or overloaded neighbor joining that segment.