Step 1: Divide the number into separate digits:
8055 => 8 0 5 5
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
8 to 0 = 8
0 to 5 = 5
5 to 5 = 0
5 to 8 = 3
Step 3: Combine the filters to a string:
8 5 0 3 = 8503