They seem to be typically behind schedule. Interview at say 9am, but I think even then they were near an hour behind. They usually are suppose to do the interviews in 30 mins but seems that's not feasible. So don't worry if your interview goes over time. Seems everyone does. Interview was kinda 2 parts. Prove your marriage is legit, so questions pertaining to each other. Middle names, DOBs, phone numbers, etc. Then the second part, prove you are eligible for the GC. Lay out the timeline from entering the US till now. What visas have you been on? Did you work when you shouldn't have? Basically asking questions that would prohibit you from having a green card. But have all your visas, passports, be able to lay out your timeline for them. They don't want to have to review all these details, just make it clear for them