it means your petition/application still at NVC it changes to IN-TRANSIT or READY once sent to the US Embassy and then you receive an appointment letter.

still in nvc it will change when u will get interview appointment

it’s at national visa center

@R B after status is ready… how long they take to send interview date?

I don't know and I don't think anyone knows. Every Embassy is different of how much slots they have for interviews monthly.