Step 1: Divide the number into separate digits:
9279 => 9 2 7 9
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
9 to 2 = 7
2 to 7 = 5
7 to 9 = 2
9 to 9 = 0
Step 3: Combine the filters to a string:
7 5 2 0 = 7520