Hi yaro,
For the date given, i don't think they may call you guys to come earlier than that. It's only when you are not given a date that they may call you to come on a date that will be okay to them. In any case just prepare and be ready for them.
I was put through adm processing and to be honest with you the anxiety was too much for me. There is no need to worry if all your documents are authentic also if you guys provided a house number on your application forms they may come around your area to enquire from your neighbors the authenticity of your marriage. In my case, we did not provide house numbers on our forms so they did not come to our area. That not withstanding, i did my home work. I remember i alerted a lady who operates a provision store in front of our house that if anybody comes looking for me; she should know what to say. It was then that she told me that a similar incidence happened two years ago, she said two guys came to our area with a picture of a guy and his wife who reside in the neighborhood and they were trying to find out if she knows them but she denied knowing them. You know in our part of the world we just don't disclose the identities of our neighbors to people we don’t know.
Regarding my experience, a call first came to me but the line wasn't clear so i could hardly hear what the person was saying. All l heard was is this ....... (my name). After ten minutes, my wife phone rang and i answered it, the person ask to speak to ....... (my wife). He asked my wife where she is and she mentioned it, my wife asked who she's speaking to and the line went dead. It was then that it occurred to me that the voice sounded like the one who called me and when i check the number, it was the same number that called my wife. Few calls came to her after-wards and in one of those calls; the person said she met my wife without a wedding ring. In a nut shell, she was trying to behave as if she met my wife some few weeks ago and she was making a follow-up call.
To conclude, there's no need to worry if you know all your documents are authentic. Just make sure you do your home work well and you will sail through. All the best.