That Hamming code is a special case of Hamming code. The total number of bits is 7, while the number of data bits is 4. It means that for error detection and correction purposes, there are 3 redundant bits, known as parity bits. The reason for its popularity as an example of a Hamming code is that it has one of the smallest sizes and possesses error correcting abilities.
The (7,4) Hamming code is an example, not a standard size
