Demo is not wrong, There are 215 (or so) days until October 4 (or month 9 in JS). Plugin uses JavaScript functions to get difference between two dates, it is not doing any calculations on it’s own.
And, date title should be October 3 (days in JS object Date are from 1 to 31). Months start from 0, days from 1, what logic JavaScript creators used here we will never know :).
Milan