Need Help! Dimensios Editing Bobad 25

Hi All,
I need to know if anyone can help with this. I am trying to draw a shaft in Bobcad 25 But I can't manually edit
the dimensions as needed. For instance, The shaft is 18" dimensioning picks it up just fine but I have to draw an 18 inch shaft...This won't print on 11 inch paper so as you can see everything good. I want to draw say 9" shaft but input the dimension as 18"

Thanks for any help.