Indicators contain values which interpret or supplement the data found in the field.
Indicator values are interpreted independently, that is, meaning is not ascribed to the two indicators taken together. Indicator values may be a lowercase alphabetic or numeric character. In a defined indicator position, a blank may be assigned a meaning, or may mean no information provided . In MARC, the valid NLR value is M Mandatory in both indicator positions for fields that include indicator positions. This includes fields 010 through 8XX and any locally-defined fields within the 010 to 999 range that may be used by a cataloging agency.