Step 1: Divide the number into separate digits:
15524 => 1 5 5 2 4
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
1 to 5 = 4
5 to 5 = 0
5 to 2 = 3
2 to 4 = 2
4 to 1 = 3
Step 3: Combine the filters to a string:
4 0 3 2 3 = 40323