MiniComm Package happen error

[jiangwei7480]

procedure TmnCommThread.Execute;
begin
  try
    while not Terminated and FCommStream.Connected do
    begin
      if not UseWait or (FCommStream.WaitRead) then;
      begin
        if not Terminated and FCommStream.Connected then
          StringArrived(FCommStream.ReadString(255)); {$Warning Why it is 255? }
      end;
    end;
  finally
  end;
end;                    

Error is function FCommStream.ReadString(255)，loss one parameter ，but stringArrived函数parameter type is string！

[JonnyTech]

Compiler? Operating system? Versions? Full code please.