Step 1: Divide the number into separate digits:
02511 => 0 2 5 1 1
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
0 to 2 = 2
2 to 5 = 3
5 to 1 = 4
1 to 1 = 0
1 to 0 = 1
Step 3: Combine the filters to a string:
2 3 4 0 1 = 23401