2. Because the data obtained is the number of colonies rather than the number of live bacteria! Because the number of live bacteria and colonies are not absolutely the same, the number of colonies cannot be equal to the number of live bacteria. For example, if I cultivate three colonies, then the result is three colonies, and it cannot be said that the result is three live bacteria. Although the number of live bacteria is similar, it is inevitable that there will be some errors depending on the operator's technology. )