Step 1: Divide the number into separate digits:
2890 => 2 8 9 0
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
2 to 8 = 6
8 to 9 = 1
9 to 0 = 9
0 to 2 = 2
Step 3: Combine the filters to a string:
6 1 9 2 = 6192