This article describes how to go from a standard table...
...to a table which adds an asterisk to every cell with a sample size lower than a specified value and a note in the footer indicating the cut off:
1. Select your table.
2. In the toolbar go to Automate > Browse Online Library > Modify Footers > Add a Footnote for Cells with Small Sample Sizes.
3. Set the Minimum Column n that will be used as the threshold (default is 30). Note, if Column n is not used in the table, Base n is used instead.
4. Press OK.