Step 1: Divide the number into separate digits:
5208 => 5 2 0 8
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
5 to 2 = 3
2 to 0 = 2
0 to 8 = 8
8 to 5 = 3
Step 3: Combine the filters to a string:
3 2 8 3 = 3283