Does all the numeric data that you are trying to sum originate from the
same Column of your Source Data?
Pivot Tables will not automatically sum numbers originating from
different columns of your source data.
For example, if your data consists of One column of Salespersons'
names, a column of dates and a column of sale amounts, you could drop
the names to the column fields area of the pivot table, the dates to
the rows area, and the amounts to the data items area, and the rows and
columns would automatically sum.
However, if your source data has a separate column for each date and
you drag all of the dates into the pivot table data item area, no grand
total will be created for your rows of data, unless you drag an
additional dimension into the column fields area, such as "geographical
region" or "product class."
If you want to sum numbers from separate columns of your source data
you need to create a formula field in the pivot table, e.g. Jan + Feb +
Mar
