docs: function parse_BrtMargins(data, length, opts) {
  	return {
  		left: parse_Xnum(data, 8),
  		right: parse_Xnum(data, 8),
  		top: parse_Xnum(data, 8),
  		bottom: parse_Xnum(data, 8),
  		header: parse_Xnum(data, 8),
  		footer: parse_Xnum(data, 8)
  	};
  }