Control the default number used by the Unique Values renderer

Summary

The default number of values used by the Unique Values renderer may be inconvenient or undesirable, and there is currently no mechanism in the interface to control this. You can, however, use the Advanced ArcMap Settings sample utility to specify the number of classes.

Procedure

1. If you have not already done so, install the Advanced ArcMap Settings tool.
   
   See: How To: Install the Advanced ArcMap Settings tool
2. Run the tool and click the Raster tab.
3. Set the 'Raster Unique Values Maximum Number of Classes' option to suit your needs. The default value is 25 and the maximum value allowed is 256.