Step 1: Divide the number into separate digits:
7003 => 7 0 0 3
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
7 to 0 = 7
0 to 0 = 0
0 to 3 = 3
3 to 7 = 4
Step 3: Combine the filters to a string:
7 0 3 4 = 7034