Step 1: Divide the number into separate digits:
15948 => 1 5 9 4 8
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
1 to 5 = 4
5 to 9 = 4
9 to 4 = 5
4 to 8 = 4
8 to 1 = 7
Step 3: Combine the filters to a string:
4 4 5 4 7 = 44547