Step 1: Divide the number into separate digits:
2088 => 2 0 8 8
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
2 to 0 = 2
0 to 8 = 8
8 to 8 = 0
8 to 2 = 6
Step 3: Combine the filters to a string:
2 8 0 6 = 2806