Step 1: Divide the number into separate digits:
2550 => 2 5 5 0
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
2 to 5 = 3
5 to 5 = 0
5 to 0 = 5
0 to 2 = 2
Step 3: Combine the filters to a string:
3 0 5 2 = 3052