Step 1: Divide the number into separate digits:
8358 => 8 3 5 8
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
8 to 3 => 5
3 to 5 => 2
5 to 8 => 3
8 to 8 => 0
Step 3: Convert distances to codes (0=E[qual],
1 & 9 = C[onsecutive], 2-8 = N[one]):
5 => N
2 => N
3 => N
0 => E
Step 4: Combine the filters to a string:
N N N E = NNNE