Step 1: Divide the number into separate digits:
07440 => 0 7 4 4 0
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 4 = 0
4 to 0 = 4
0 to 0 = 0
Step 3: Combine the filters to a string:
7 3 0 4 0 = 73040