Step 1: Divide the number into separate digits:
4624 => 4 6 2 4
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
4 to 6 = 2
6 to 2 = 4
2 to 4 = 2
4 to 4 = 0
Step 3: Combine the filters to a string:
2 4 2 0 = 2420