Step 1: Divide the number into separate digits:
3830 => 3 8 3 0
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
3 to 8 => 5
8 to 3 => 5
3 to 0 => 3
0 to 3 => 3
Step 3: Convert distances to codes (0=E[qual],
1 & 9 = C[onsecutive], 2-8 = N[one]):
5 => N
5 => N
3 => N
3 => N
Step 4: Combine the filters to a string:
N N N N = NNNN