There is small cosmetic bug:\
place ad with non default "Length of Ad:" value (for example 30 Days). When all will be done open just posted ad and try to modify it (you can not change anything here and go to the next step).\
Open "Preview Ad" page and look at "Length of Ad:" field there - it will show the default value (7 Days in my case) instead of real 30 days. Bug actual only for Preview page but user may be confused here.