This field contains the ID of the font that is used to display a dining table row in the Dining Allocation panel that is joined to a group of tables and is not the main table of the joined group of tables. If this field is blank, the dining table row has the font associated with the allocation status of the main table.
There are some actions that are not valid for a joined table. Therefore, having a special font for this table, for example italics and light gray color, helps the user identify the joined table as such.