Step 1: Divide the number into separate digits:
0747 => 0 7 4 7
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
0 to 7 = 7
7 to 4 = 3
4 to 7 = 3
7 to 0 = 7
Step 3: Combine the filters to a string:
7 3 3 7 = 7337