Step 1: Divide the number into separate digits:
9029 => 9 0 2 9
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
9 to 0 = 9
0 to 2 = 2
2 to 9 = 7
9 to 9 = 0
Step 3: Combine the filters to a string:
9 2 7 0 = 9270