Step 1: Divide the number into separate digits:
8371 => 8 3 7 1
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
8 to 3 = 5
3 to 7 = 4
7 to 1 = 6
1 to 8 = 7
Step 3: Combine the filters to a string:
5 4 6 7 = 5467