When showing graphs of larger time ranges, the graphs are normally based on aggregated values, which means multiple measured values are consolidated to a single value.
For example, when a graph is based on the "max" aggregation function, like nearly all graphs are by default, the values in the Average column are not the real average values of the shown time, but the average values of the max values in the step of the graph. The step of the graph is now shown on the top right of the graph.
To clarify this: If you look at a 7 day graph, you have a step of 30 minutes. If the service is being checked in a 1 minute interval, the graph is based on the maximum of 30 single values of each 30 minutes step. So your average values are the 7 day average of the 30 minute maximum values.
This is obviously not what most users would expect, but we would have to fetch 3 times more data per graph to get the real average and the real min values for each graph. The graphs are already producing a lot of load and we try to keep the impact low, so we decided to make the calculation transparent and changable by the user.
If you have a max graph, the min and average columns are slightly grayed out to visualize the situation. If you hover on the titles, you get a description about it. Now you can click on the columns titles to change the aggregation function the graph is based on.