"I'm almost a grown up"

Last night while talking to me Isabelle announced, "Mom, I'm almost a grown up!" 

I asked how she figured that. She said "after 7, comes 8, after 8, 9, after 9, 10, 11, 12, 13, 14 , 15, 16, 17, 18, 19, 20, and then I'm a grown up!"