What is the blue line in the Network Latency Graph?

Hi,

during the play I do get the symbol for packet loss and the game is lagging. So I activated the network graphs for troubleshooting. Then I realized that the graphs do not show packetloss at all but there is a blue line in the latency graph that is jumping up and down to the times that the game is lagging. To me the LAT (green) and ALAT (red) look good and stable and there is no discription of the blue line. 

Can someone explain waht this blue line is?

Thanks a lot in advance.

Best