Step 1: Divide the number into separate digits:
2708 => 2 7 0 8
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
2 to 7 = 5
7 to 0 = 7
0 to 8 = 8
8 to 2 = 6
Step 3: Combine the filters to a string:
5 7 8 6 = 5786