Step 1: Divide the number into separate digits:
2306 => 2 3 0 6
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
2 to 3 = 1
3 to 0 = 3
0 to 6 = 6
6 to 2 = 4
Step 3: Combine the filters to a string:
1 3 6 4 = 1364