FileStream.Seek如何不对

FileStream.Seek怎么不对？
procedure TForm1.Button1Click(Sender: TObject);
var
  fs: TFileStream;
  Buffer:array[0..100] of byte;
begin
  fs := TFileStream.Create(filename, fmOpenRead);
  try
  fs.Seek($400000, soFromBeginning);
  fs.Read(Buffer, 100);
  memo1.Lines.Add(bytearraytohex(buffer));
  finally
  fs.Free;
  end;
end;
这段代码怎么读出来是$800000这个地址的值呢？

[解决办法]
要读出来是$800000这个地址的值, 那就应该是: fs.Seek($800000, soFromBeginning);