Logstash 2.1.0 : Kafka Output (JMX)

Hi,
I've been watching the behaviour of the logstash-kafka-output producer via JMX and it appears that it reports the outbound message rate to kafka incorectly for producer-topic-metrics.

Basically I'm seeing that it reports the record-send-rate as being half that reported by kafka for inbound messages on that topic and by the logstash-kafka-input consumer...

Regards,
David