System-network-in-bytes-dropped - timeframe

[kafe]

Can you please give me an exact timeframe during which the system-network data was collected in this example? https://www.elastic.co/guide/en/beats/metricbeat/current/metricbeat-metricset-system-network.html
{
"@timestamp": "2017-10-12T08:05:34.853Z",
"agent": {
"hostname": "host.example.com",
"name": "host.example.com"
},
"event": {
"dataset": "system.network",
"duration": 115000,
"module": "system"
},
"metricset": {
"name": "network"
},
"service": {
"type": "system"
},
"system": {
"network": {
"in": {
"bytes": 37904869172,
"dropped": 32,
"errors": 0,
"packets": 32143403
},
"name": "wlp4s0",
"out": {
"bytes": 6299331926,
"dropped": 0,
"errors": 0,
"packets": 13362703
}
}
}
}

We've got the "@timestamp": "2017-10-12T08:05:34.853Z" and the duration defined here - 115000 (nanoseconds?).
What does the duration exactly mean here please?
What is the start of the data collection - in other words: we've got number of bytes dropped here - since when? What is the reset to 0 time?

[Kaiyan_Sheng]

event.duration here is Duration of the event in nanoseconds: https://www.elastic.co/guide/en/ecs/current/ecs-event.html

The timestamp represents when this event was collected so the data shown here happened at 2017-10-12T08:05:34.853Z.