Step 1: Divide the number into separate digits:
30891 => 3 0 8 9 1
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
3 to 0 = 3
0 to 8 = 8
8 to 9 = 1
9 to 1 = 8
1 to 3 = 2
Step 3: Combine the filters to a string:
3 8 1 8 2 = 38182