For example, let's say you include two phone numbers per record in a constituent import file.

Each phone number comprises up to four columns of data in the import file with these headers: PhoneAddrImpID, PhoneImpID, PhoneNum, and PhoneType. Columns will be grouped based on phone numbers but will have the same header. On the import's Fields tab, use the Extension column to group the import fields correctly. In our example, the first grouping has an 00 extension and the second has an 01 extension.

Version 7 Import Extensions