The up-to-date F.A.Q. page for PHPExcel can be found on http://www.codeplex.com/PHPExcel/Wiki/View.aspx?title=FAQ&referringTitle=Requirements.
This is normal behaviour of the compatibility pack, Excel2007 displays this correctly. Use PHPExcel_Writer_Excel5 if you really need calculated values, or force recalculation in Excel2003.