The documentation for the ISAM Filters had a minor discrepancy between SETFLTR() and SETFLTRN() regarding the first parameter:
SETFLTR:
COUNT SetDataFilter(COUNT datno, pTEXT condexpr)
SETFLTRN:
COUNT ctDECL SETFLTRN(COUNT filno, UCOUNT fltnum, UCOUNT fltopts, pTEXT expression);
The documentation and the descriptions in the code have been changed to name this parameter datno instead of filno. The use of the parameter datno indicates these functions operate over a data file only. When filno is used, it indicates the function can operate over a data file and and index file.