their names. The supported areas are:
@itemize @bullet
-@item
-Areas that correspond to parts of @dfn{subtables}, whose contents are
-the cells that pair an innermost row variable and an innermost column
-variable:
-
-@table @code
-@item ROW
-A row within a subtable.
-
-@item COL
-A column within a subtable.
-
-@item SUBTABLE
-All the cells in a subtable
-@end table
-
@item
Areas that correspond to parts of @dfn{sections}, where stacked
variables divide each section from another:
@item LAYERCOL
A column in one layer within a section.
@end table
+
+@item
+Areas that correspond to parts of @dfn{subtables}, whose contents are
+the cells that pair an innermost row variable and an innermost column
+variable within a single layer. A section can contain multiple
+subtables and a subtable is always within a single section:
+
+@table @code
+@item ROW
+A row within a subtable.
+
+@item COL
+A column within a subtable.
+
+@item SUBTABLE
+All the cells in a subtable.
+@end table
+
@end itemize
The following summary functions may be applied to any variable