Author Ratings for Articles

Hello good people. Have you any problems with your poem ratings? Most of mine are U which I believe to be Universal, for all ages. PG would be Parental Guidance, right? Then the higher numbers to 18 would be the highest degree of adult content, right?

Lately I have neglected to really check my poems as to whether they are on U. Then I find out somehow the/my computer kicked the rating into 18 which I did not notice. So I have been going backwards to fix them, since I have never written explicit and/or offensive material. Cheers.