Each node represents an application; the size is how often it was run.
The size of its pie slice is how often it was run with this app (numactl).
A dashed arrow between nodes shows that these
applications happened to be used by the same user on the same day, and that one
was started after the previous one completed. For example maybe
in order to achieve a goal, a researcher had to run application
A, then process results with application B; the graph would show an arrow from
A to B.