Step 1: Divide the number into separate digits:
3708 => 3 7 0 8
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
3 to 7 = 4
7 to 0 = 7
0 to 8 = 8
8 to 3 = 5
Step 3: Combine the filters to a string:
4 7 8 5 = 4785