Number of messages per plane

A plane passed through here this morning that sent tallied almost 33000 messages. At a rate of one transmission per second the plane would need to be visible for about 9 hours. What am I missing here? :confused:

My stats pages shows an average of 6.3 per A/C per second.
(I have collectd running, installed by Joe’s scripts).
TCAS generates a lot of messages, especially in busy areas.