Variable data fields:
The variable data fields are all other variable fields, excluding the 00X series. They may vary in length and may contain any text or other data needed to describe an individual classification item or other type of record. In addition to being identified by a field tag in the Directory, variable data fields contain two kinds of content designation: two indicator positions stored at the beginning of each field and a two-character subfield code preceding each data element within the field.
For more information, see: