Step 1: Divide the number into separate digits:
4887 => 4 8 8 7
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
4 to 8 = 4
8 to 8 = 0
8 to 7 = 1
7 to 4 = 3
Step 3: Combine the filters to a string:
4 0 1 3 = 4013