Step 1: Divide the number into separate digits:
6727 => 6 7 2 7
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
6 to 7 = 1
7 to 2 = 5
2 to 7 = 5
7 to 6 = 1
Step 3: Combine the filters to a string:
1 5 5 1 = 1551