Step 1: Divide the number into separate digits:
0675 => 0 6 7 5
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
0 to 6 = 6
6 to 7 = 1
7 to 5 = 2
5 to 0 = 5
Step 3: Combine the filters to a string:
6 1 2 5 = 6125