Step 1: Divide the number into separate digits:
9470 => 9 4 7 0
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
9 to 4 = 5
4 to 7 = 3
7 to 0 = 7
0 to 9 = 9
Step 3: Combine the filters to a string:
5 3 7 9 = 5379