Number of LBT-RM datagrams unrecovered due to a retransmission not received
within the NAK generation interval (LBT-RM only)

- n (Int32)
- Statistics set index

Number of LBT-RM datagrams unrecovered due to a retransmission not received
within the NAK generation interval.

This is set by configuration option transport_lbtrm_nak_generation_interval;
default 10,000ms. Note: Receivers for these messages' topics will also report
related messages as unrecoverable, with LBM_MSG_UNRECOVERABLE_LOSS for an
individual message and LBM_MSG_UNRECOVERABLE_LOSS_BURST for a burst loss
event. However, it is possible for these application-level message
declarations to occur even without increments to this counter, as the
transport is unaware of the topic content of messages and may still be trying
to deliver related lost packets.
This method returns a value from the nth set of statistics
encapsulated within this object.