What does the blue lines mean?

Openfire Openfire Support
1

I cann’t find out any point for the blue lines in the picture.

Or is there any clue I can follow?

The traffic is Server->Statistics->All Reports->Server Traffic.

The pluign named Load Statistic is needed.

2

I assume it is either IN or OUT traffic, one may need to lookup the source code or javadoc.

3

The orange one may be IN, and the blue one may be OUT.

Great hypothesis.