@item @code{COUNT} (``Count'')
The sum of weights in a cell.
+If @code{CATEGORIES} for one or more of the variables in a table
+include missing values (@pxref{CTABLES Per-Variable Category
+Options}), then some or all of the categories for a cell might be
+missing values. @code{COUNT} counts data included in a cell
+regardless of whether its categories are missing.
+
@item @code{@i{area}PCT} or @code{@i{area}PCT.COUNT} (``@i{Area} %'')
A percentage within the specified @var{area}.
A percentage of total values within the specified @var{area}.
@end table
-The following summary functions apply only to scalar variables:
+The following summary functions apply only to scalar variables or
+totals and subtotals for categorical variables. Be cautious about
+interpreting the summary value in the latter case, because it is not
+necessarily meaningful; however, the mean of a Likert scale, etc.@:
+may have a straightforward interpreation.
@table @asis
@item @code{MAXIMUM} (``Maximum'')
The sum.
@item @code{TOTALN} (``Total N'')
-The sum of total count weights.
+The sum of weights in a cell.
+
+For scale data, @code{COUNT} and @code{TOTALN} are the same.
+
+For categorical data, @code{TOTALN} counts missing values in excluded
+categories, that is, user-missing values not in an explicit category
+list on @code{CATEGORIES} (@pxref{CTABLES Per-Variable Category
+Options}), or user-missing values excluded because
+@code{MISSING=EXCLUDE} is in effect on @code{CATEGORIES}, or
+system-missing values. @code{COUNT} does not count these.
@item @code{VALIDN} (``Valid N'')
-The sum of valid count weights.
+The sum of valid count weights in included categories.
+
+@code{VALIDN} does not count missing values regardless of whether they
+are in included categories via @code{CATEGORIES}. @code{VALIDN} does
+not count valid values that are in excluded categories.
@item @code{VARIANCE} (``Variance'')
The variance.