Two types of tests are reflected on the VoIP Quality Tab — an end-to-end test and a hop-by-hop test.  The MOS, jitter, latency, and packet loss results of each end-to-end test are reflected on the upper graph and best represent the quality of a VoIP call across the entire data path during the test interval.  

RTP over Time

Clicking on any upper test results will generate a subway map below and show hop-by-hop test results correlating to the same timestamp. 

Subway Map of WAN Hops

The hop-by-hop test discovers the routers in the data path and determines if any router can be identified as contributing significantly to jitter, latency, or packet loss during the testing interval.  The hop-by-hop results are not based on VoIP call testing as the intermediate routers are not VoIP call agents, but solely packet forwarders.  Because they are distinct tests, packet loss and jitter results will be different.