Is expected date of delivery 100% accurate or counted on average days by LMP

Your scan report will be more precise though No one can say only on the fixed date it would happen.

Scan dates are tentative date for Ur delivery. It's ideal time needed for baby full Growth. .
But baby can be ready anytime near this date.

Hi nothing is accurate. Anytime after 37 weeks you can expect to deliver, from the due date 15 days up or front is normal.