Step 1: Divide the number into separate digits:
8930 => 8 9 3 0
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
8 to 9 = 1
9 to 3 = 6
3 to 0 = 3
0 to 8 = 8
Step 3: Combine the filters to a string:
1 6 3 8 = 1638