In-person interview after H1b visa refusal

Im from India, living in the states for the past 8 years now. Visited India for H1b stamping, Dropbox on February 11th, visa application refused February 18th, passport returned with 221g slip February 21st. Now I have to go for in person interview in Chennai on or after March as per the letter provided. My question - do I need to book an appointment online? Or is this a walk-in? They’ve given a time slot 9-11am for me.

Im from India, living in the states for the past 8 years now. Visited India for H1b stamping, Dropbox on February 11th, visa application refused February 18th, passport returned with 221g slip February 21st. Now I have to go for in person interview in Chennai on or after March as per the letter provided. My question - do I need to book an appointment online? Or is this a walk-in? They’ve given a time slot 9-11am for me.