Step 1: Divide the number into separate digits:
02817 => 0 2 8 1 7
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
0 to 2 = 2
2 to 8 = 6
8 to 1 = 7
1 to 7 = 6
7 to 0 = 7
Step 3: Combine the filters to a string:
2 6 7 6 7 = 26767