None
An integer, smaller or equal to 32, whose value is the length of the binary representation of the counter i when i is an input in counter mode or (optionally) in feedback mode and double-pipeline iteration mode of each iteration of the PRF.
Source(s):
NIST SP 800-108
The number of blocks in the formatted input data (N, A, P).
Source(s):
NIST SP 800-38C