Step 1: Divide the number into separate digits:
89690 => 8 9 6 9 0
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
8 to 9 = 1
9 to 6 = 3
6 to 9 = 3
9 to 0 = 9
0 to 8 = 8
Step 3: Combine the filters to a string:
1 3 3 9 8 = 13398