Step 1: Divide the number into separate digits:
8533 => 8 5 3 3
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
8 to 5 = 3
5 to 3 = 2
3 to 3 = 0
3 to 8 = 5
Step 3: Combine the filters to a string:
3 2 0 5 = 3205