Step 1: Divide the number into separate digits:
0986 => 0 9 8 6
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
0 to 9 = 9
9 to 8 = 1
8 to 6 = 2
6 to 0 = 6
Step 3: Combine the filters to a string:
9 1 2 6 = 9126