How application endpoint request time taken is calculated?

Hi Team,
I am using GrafanaCloud fortracing. I have configured OTEL collector agent to send the traces to Grafana Cloud. OpenTelemetry data is sent from [ASP.NET] applications on the same host and the agent sends data to the (Tempo endpoint) cloud.

Able to see the traces on the Grafana dashboard with table & time series data visualization.

My application flow will be like,
Login page → establish websocket connection to the WCF endpoint → once connected perform file copy paste to the remote drive

So this request would go more subsequent calls to other applications and perform some operations.

So need to know how the each application request timestamp is calculated?