Step 1: Divide the number into separate digits:
61500 => 6 1 5 0 0
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
6 to 1 = 5
1 to 5 = 4
5 to 0 = 5
0 to 0 = 0
0 to 6 = 6
Step 3: Combine the filters to a string:
5 4 5 0 6 = 54506