Ad positions

Hello,
I have installed your plugin and it is working well. However, it is only showing two ads (when I want to save three it shows a 404 error).

At the moment on my home page I have 3 ads because the third is controlled by another plugin. How can I show 3 just with your plugin?

Also, can I use different positions than the ones suggested?

http://ibcbaccarat.com/

Thank you!

https://wordpress.org/plugins/google-publisher/