Hi suchil,
Open file Constant.js ( CuteSoft_Client\CuteEditor\Scripts\Constant.js)
Find section below
editorconstant._CreateEditingTableStyle = "<table border='0' cellspacing='2' cellpadding='2' width='500'>";
Change to
editorconstant._CreateEditingTableStyle = "<table border='0' cellspacing='2' cellpadding='2' width='750'>";
Clean the browser cache and try
Regards,
Ken