This article describes how to go from a standard table...
...to a table with an additional column that computes the difference between specified columns:
A table with multiple columns.
1. Select your table.
2. Go to Properties > RULES on the object inspector.
3. To apply the rule, select the Plus (+) > Browse Online Library > Table Computations > Difference Between a Pair of Columns.
4. OPTIONAL: Select the Statistic to use (if different from the default).
5. Select the column under Column 1 to compute the difference from.
6. Select the column under Column 2 to compare against.
7. Press OK.
This rule calculates then the difference between these two columns and displays it to the right of the second column. Note, this rule can only apply to a single statistic and no significance tests are conducted on these cells. It is also not compatible with tables that have column spans.
Note, if you select Switch rows and columns on your table, the rule will no longer work due to the table dimensions changing. In this case, you will have to apply the Difference Between a Pair of Rows rule instead.