I got 221g for h1b and asked me to submit the client letter and I have submitted the client letter on 2nd-May-2018 and they haven't reach to client for verification and when I called to NVC (+1603-334-0888) they are saying that thee is the note which say that embassy will call you for second interview. I have few question on second interview.
1) How much time they take to call me for second interview
2) Why they call for second interview, it is a positive sign
3) Why they haven't done my client verification.