Well, I don't see what you want to do.
In your screenshots, I see that you added a read more in the description, and that it then displays in the description on the product page. Which is what it is supposed to do.
Do you want it to do something in particular on the product page ? Maybe like in the show_tabular view ? Have a small description and the rest below ? In that case, there is no option for that and you'll have to add custom code in the view files of the product view via the menu Display>Views to handle that yourself.