Step 1: Divide the number into separate digits:
0074 => 0 0 7 4
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
0 to 0 = 0
0 to 7 = 7
7 to 4 = 3
4 to 0 = 4
Step 3: Combine the filters to a string:
0 7 3 4 = 0734