Step 1: Divide the number into separate digits:
4938 => 4 9 3 8
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
4 to 9 = 5
9 to 3 = 6
3 to 8 = 5
8 to 4 = 4
Step 3: Combine the filters to a string:
5 6 5 4 = 5654