Step 1: Divide the number into separate digits:
7093 => 7 0 9 3
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
7 to 0 = 7
0 to 9 = 9
9 to 3 = 6
3 to 7 = 4
Step 3: Combine the filters to a string:
7 9 6 4 = 7964