I have openlitespeed server that runs over QUIC.
I want to download file from the server, and get from the access logs of the server the time to serve the request (%D in the logs format).

In my case some of the files are very small – around 100 bytes.

For such small files I found that the request time can be very long, 100 millisecond which there is no reason for such long time, the RTT is around 30 millisec.
On the other have sometimes the request time can be supper short, less around 100 microsecond, and in this case, how can the request time be shorter than the the RTT?

Is there a good explanation for such behaviour?

I tried to find some documentation about the way openlitespeed or apache HTTP server calculates this metric with no success.

If there is some good documentation, I would be glad for a reference.