Step 1: Divide the number into separate digits:
5485 => 5 4 8 5
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
5 to 4 = 1
4 to 8 = 4
8 to 5 = 3
5 to 5 = 0
Step 3: Combine the filters to a string:
1 4 3 0 = 1430