Step 1: Divide the number into separate digits:
5393 => 5 3 9 3
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
5 to 3 = 2
3 to 9 = 6
9 to 3 = 6
3 to 5 = 2
Step 3: Combine the filters to a string:
2 6 6 2 = 2662