first, you arrange all the numbers in ascending sequence, you should get:
62, 64, 65, 65, 67, 68, 68, 69, 69, 69, 70, 70, 70, 71, 71, 71, 73, 72, 72, 73
yes and now you can see there are 20 values all arranged in ascending order. from here, you find the 2 middle values since it is an even number.
it should be value 10 and 11 which is number 69 and 70
now you find the average which is:
= 69.5
so your center value is 69.5.