Step 1: Divide the number into separate digits:
4079 => 4 0 7 9
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
4 to 0 = 4
0 to 7 = 7
7 to 9 = 2
9 to 4 = 5
Step 3: Combine the filters to a string:
4 7 2 5 = 4725