Each new branch will grow two renewable branches in the next time and one non-renewable branch in the next time.

Because the number of non-updatable branches does not affect the number of updatable branches (this sentence is the key), the non-updatable branches can be ignored first, so the nth graph grows 2 (n- 1) more updatable branches than the nth graph.

Looking at non-updatable branches, the nth graph has 1/4 * 2 (n- 1) non-updatable branches more than the nth graph.

Therefore, Figure 7 has 2 6+1/4 * 2 6 = 80 more branches than Figure 6.