The Score graph

A couple of times an hour the pool system checks the time from your server and compares it to the local time. Points are deducted if the server can't be reached or if the time offset is more than 100ms (as measured relatively crudely from the monitoring systems). More points are deducted the bigger the offset is.

When the score goes down the background color in the top part of the chart will reflect how severely the "outage" is. The color scale goes from blue (very little) to yellow to orange to red (the server is several seconds off or unreachable). Because of how the graph is averaged out, you can't always infer what happened from the color. It's only meant as a tool to visualize trends. For more exact details of what the monitoring system found you can click on the CSV link.

The Offset graph

The monitoring system works roughly like an SNTP (RFC 2030) client, so it is more susceptible by random network latencies between the server and the monitoring system than a regular ntpd client would be. In other words: Don't be alarmed by the occasional large offset and please don't use the offset as an absolute performance metric.