Step 1: Divide the number into separate digits:
0958 => 0 9 5 8
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
0 to 9 = 9
9 to 5 = 4
5 to 8 = 3
8 to 0 = 8
Step 3: Combine the filters to a string:
9 4 3 8 = 9438