Number of events in logstash node stats on pipelines

Hi,

when viewing logstash node stats, in particular the number of events. then I get reasonable high numbers on the 'in' and 'out' values.

Eg. on a logstash 6.7

# curl -s  -XGET 'localhost:9600/_node/stats/pipelines' | jq '.pipelines.main.events'
{
  "in": 1495916590,
  "duration_in_millis": 4857832463,
  "out": 1495916426,
  "filtered": 1495916426,
  "queue_push_duration_in_millis": 761977782
}

What's the formatting on these numbers ? What is the maximum value ?
After reaching max, does it start counting again from zero ?

KR, Ben