Number of NAKs this source transport has not processed because it met its
retransmission rate limit (LBT-RM only).

- n (Int32)
- Statistics set index

Number of NAKs this source did not process because doing so would
exceed its retransmit rate limit.

This rate limit is controlled by the transport's retransmit_rate_limit,
default 5 Mbps. The source queues the retransmission and sends an
NCF with the reason code set to "rx_delay". If naksIgnoredRetransmitDelay
is high, one or more crybaby receivers may be clogging the source's
retransmission queue.
This method returns a value from the nth set of statistics
encapsulated within this object.