Step 1: Divide the number into separate digits:
0660 => 0 6 6 0
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
0 to 6 => 6
6 to 6 => 0
6 to 0 => 6
0 to 0 => 0
Step 3: Convert distances to codes (0=E[qual],
1 & 9 = C[onsecutive], 2-8 = N[one]):
6 => N
0 => E
6 => N
0 => E
Step 4: Combine the filters to a string:
N E N E = NENE