At the call of fork, a child process is created which executes the same code of the parent from that point. The return value of fork is 0 for the child and is child pid (not 0) for the parent and this value is used to distinguish between child-parent while writing code using fork.
Thus 5 child processes are created. Since the question asks for "total number of processes created" we must include parent also making this 6 processes in total,