Step 1: Divide the number into separate digits:
68881 => 6 8 8 8 1
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
6 to 8 = 2
8 to 8 = 0
8 to 8 = 0
8 to 1 = 7
1 to 6 = 5
Step 3: Combine the filters to a string:
2 0 0 7 5 = 20075