Step 1: Divide the number into separate digits:
9319 => 9 3 1 9
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
9 to 3 = 6
3 to 1 = 2
1 to 9 = 8
9 to 9 = 0
Step 3: Combine the filters to a string:
6 2 8 0 = 6280