In hamming code, there are 4 bits of original data & 3 bits of redundant bits. N = M+K, here, N = codewords/full message, M=Datawords/Original Message & K = Redundant bits. So, N = 4+3, = 7 bits.
Burst Error: A burst error means when 2 or more bits in the data unit have changed.
Burst Error Length: The length from starting left-end corrupted bit to right-end corrupted bit in a data unit is called Burst Error Length.