Step 1: Divide the number into separate digits:
2475 => 2 4 7 5
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
2 to 4 = 2
4 to 7 = 3
7 to 5 = 2
5 to 2 = 3
Step 3: Combine the filters to a string:
2 3 2 3 = 2323