Arrived at the consolute at around 7:45am, they let me in right away, gave me a ticket marked with "9" on it and told me go to window #9 when we were allowed to go up to the 19th floor. Few people were already seating in the waiting area in the basement when I went down there.
At 8:00am, one of the security personnel led us up to the 19th floor. Window 9 is on the right of the elevator. The lady seating behind the window took my interview letter and the ticket, told me to wait for my name to be called.
At 8:15am, I got called to go to window 10. This time it was a guy. He took my passport, passport picture, pre-paid envelope, and medical exam. He went through the DS-230 with me, he asked what do I do, what does my spouse do, when did we get married. Afterward, he told me to wait for my name to be called again.
At 8:40am, I heard my name, and this time it was room 8. It is a closed-door room, but when I walked in, it is another window
All 3 people that interviewed me were nice and friendly, they even joked with me.
I hope this information will help others in the future.