Step 1: Divide the number into separate digits:
9048 => 9 0 4 8
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
9 to 0 = 9
0 to 4 = 4
4 to 8 = 4
8 to 9 = 1
Step 3: Combine the filters to a string:
9 4 4 1 = 9441