<p>Is the index value of the first record in a dbf file 0 or 1?  Is the index zero-based?</p>

i'm not sure but this might give you a clue.
http://www.dbase.com/knowledgebase/int/db7_file_fmt.htm
1.3.1 Standard Property and Constraint Descriptor Array
Table field offset - base one. 01 for
    the first field in the table, 02 for
    the second field, etc. Note: this will
    be 0 in the case of a constraint.