Step 1: Divide the number into separate digits:
6474 => 6 4 7 4
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
6 to 4 = 2
4 to 7 = 3
7 to 4 = 3
4 to 6 = 2
Step 3: Combine the filters to a string:
2 3 3 2 = 2332