You are not looking in the right place. The script 'std.fileipload1.inc' calls the initialiseFileUpload() method which in turn calls the _cm_initialiseFileUpload() method in your application table class. This is where you specify the parameters, such as:
function _cm_initialiseFileUpload ($fieldarray)
// perform any initialisation before displaying the File Upload screen.
{
$this->upload_subdir = 'pictures';
$this->upload_filetypes = array('image/x-png', 'image/gif');
$this->upload_maxfilesize = 100;
return $fieldarray;
} // _cm_initialiseFileUpload