A statement should be added saying that the current number of students is non-zero. If the current number is zero then adding 4 would be different than adding 12.
If you have 4 or 12 students in the class, you are still NOT able to divide them into teams of 8. Only classes, where the number of students is a multiple of 8, can be divided into such groups: 8 (1 team), 16 (2 teams), 24 (3 teams), etc.
There could not be 0 students in the class initially, because it would contradict either statement.