Step 1: Divide the number into separate digits:
85508 => 8 5 5 0 8
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
8 to 5 = 3
5 to 5 = 0
5 to 0 = 5
0 to 8 = 8
8 to 8 = 0
Step 3: Combine the filters to a string:
3 0 5 8 0 = 30580