The first interview - do you mean the submission of physical documents? Based on your context that’s what I suspect. If so, there’s not really an interview there, just document submission. You’ll submit your documents, the clerk will take them and check, and then someone from DOS will review your documents and walk you through the process. This part was fast, it was a little over a year ago so I don’t recall exactly but probably not more than 1.5 with waiting.
The interview that’s just the beneficiary will happen after you pass the background checks, receive your Packet 3 in the mail, do medical exam and other paperwork (collecting the civil documents can be a real potential bottleneck depending on the complexity of your case)
Glad the post can be of help—feel free to reach out if you need any other info, I don’t always get notices on thread replies.