Step 1: Divide the number into separate digits:
8312 => 8 3 1 2
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
8 to 3 = 5
3 to 1 = 2
1 to 2 = 1
2 to 8 = 6
Step 3: Combine the filters to a string:
5 2 1 6 = 5216