Some ZIP codes have multiple postal regions. The error value indicates that multiple cities share this ZIP code address. To ensure that you always receive a mileage from this area, you may want to use Default ZIP Code processing. Within the MileMaker program, go to the FEATURES menu, select Route Processing Options, and turn on Default ZIP Code processing. This will enable the system to select the default city where the post office is located. For Practical Routes, this may be a junction or suburb nearest the actual ZIP Code district.