On the 'Unique values' symbology dialog box, when selecting a field and pressing the 'Add all values' button, and the field has coded domains defined, the method adds all domain codes, even if some codes are not present in the data. This also occurs for subtype fields.
A related problem is that frequencies are not calculated for these types of fields; instead, the Count column on the 'Unique values' symbology dialog box is populated with question marks.
This problem only occurs with geodatabase data, and only if the value field has coded domains defined or is the subtype field. In this scenario, the unique-values-symbology method does not parse the data to determine all unique values; instead, all the coded domains (or subtypes) are added. Values are added even if there are no features present in the data that fall into a particular coded domain or subtype.
Conversely, if there are features in the data that do not fall into a subtype/coded domain, they will not be added to the renderer.
Finally, because the data are not being parsed upon pressing 'Add all values,' the 'Unique values' dialog box does not display counts by default.