Step 1: Divide the number into separate digits:
7596 => 7 5 9 6
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
7 to 5 = 2
5 to 9 = 4
9 to 6 = 3
6 to 7 = 1
Step 3: Combine the filters to a string:
2 4 3 1 = 2431