Step 1: Divide the number into separate digits:
8339 => 8 3 3 9
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
8 to 3 = 5
3 to 3 = 0
3 to 9 = 6
9 to 8 = 1
Step 3: Combine the filters to a string:
5 0 6 1 = 5061