about establishing ranges that results no records

I'm trying to work with ranges (dephi 1.0) but I've found that when there
are no records
in the range, it appears one record that not verifies the range established
with the fllowing sentences:
     with Table1 do begin      
        IndexName:='ByFirstSecond'  {two differents fields}
        SetRangeStart;
        Fields[0].AsValue:=12;
        Fields[1].AsValue:=18;
        SetRangeEnd;
        Fields[0].AsValue:=12;
        Fields[1].AsValue:=18;
        ApplyRange;
        First;
   end;

Resulting of this sentences it appears (only) one record with values out of
the range
established. Please if someone knows what happens reply my anwer. My
address is jbo...@redestb.es. Thank you.