code: function parse_Guts(blob) {
  	blob.l += 4;
  	var out = [blob.read_shift(2), blob.read_shift(2)];
  	if(out[0] !== 0) out[0]--;
  	if(out[1] !== 0) out[1]--;
  	if(out[0] > 7 || out[1] > 7) throw new Error("Bad Gutters: " + out.join("|"));
  	return out;
  }
docs: /* [MS-XLS] 2.4.134