It helps you organize the graph
It is useful to print and tape up next to the computer for QUICK REFERENCE WHILE BUILDING LAYOUTS.
a. So you can have detailed notes about individual tables
b. You can drag the TABLE OCCURRENCES right on top of a note to create a VISUAL GROUPING
c. You can make a NOTE as wide as the graph, with nothing more than a headline describing what kind of data is in the table occurrences directly underneath.