Unfortunately, if it's the day of the event you had reserved tickets for, you won't be able to decline your tickets. It's simply too short notice to offer your tickets to the next member on the waitlist. You have up until several hours before the event to decline your tickets. After that point, the list is locked. You cannot reduce the number of tickets you had reserved, either.
Your attendance percentage will be reduced if you do not attend, and since the list is locked, we are unable to decline your tickets either. We count on the 1iota members who reserve their tickets to use them, and if they don't, that will be reflected in their attendance percentage.