Step 1: Divide the number into separate digits:
90651 => 9 0 6 5 1
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
9 to 0 = 9
0 to 6 = 6
6 to 5 = 1
5 to 1 = 4
1 to 9 = 8
Step 3: Combine the filters to a string:
9 6 1 4 8 = 96148