Each timestamp is when the server generated a response. There should be one
every second. The milliseconds values after that are a combination of clock
difference plus latency, first from client to server and secondly from server
to client. Finally, your observed IP address is reported.
Note: If the time is not synchronised or the offset is incorrect, only the total will be correct.
Also note that the uplink latency might be way off, since your browser might be establishing a new TCP+TLS connection for every ping. If the uplink latency is 3x the downlink latency
or more, this is probably the case. You can avoid this by trying the websocket version instead. Firefox 77 was tested to not have this problem; it re-uses the connection.
Server-side processing is about 2.2ms.