Help needed in filling G-325a form

[Ilovemywife]

I am green card holder and I am recently married abroad. I am trying to file petition for my wife and I am confused how to fill G-325a form. In our marriage certificate my surname has NOT been mentioned on her name. So while filling her G-325a, in 1st line and last line, do I have to add my surname on her name or Do I have to mention her previous surname only?
I will really appreciate if you guys can suggest me.

Thanks in advance.