QoS and Event Trace Logs

We’ve been testing for 3 months the CloudXR in Amazon AWS and we’ve got a few questions about the QoS logs:
1 - How often does the log write into QoS data, Depends on what? (not per frame)
2 - Is the latency just for the network? (from server to client or for what)
3 - How is it possible that the latency is often 0.0 ms?
4 - Is the jitter just for the network?
5 - What does the round trip delay refer to?
and about the Event Trace Logs:
6 - In case of the client’s ETL, the first frame ID is 140 (or 160), why?
7 - Server’s and client’s ETL time is not the time, when we measure, how can it be setted?
8 - Sometimes the ETL log is too short; it logs for 2 minutes only, however, we measured for 3 minutes. Why is this?

Thank you in advance!