B2 Visa Renewal White Slip

My parents who already have a 10 year multiple entry visa that is slated to expire in September 2022. They have been to USA multiple times and have left before the 6 months timeframe every visit but the last one. They had to over stay for 2.5 months due to non availability of flights due to COVID. We applied for their I539 and it was approved as well.

They applied for B2 visa renewal via dropbox on april 18 2022. They had submitted their passports. On May 9th my mother received an SMS to come collect her documents. When they went in person, they found that she had been given a 221g white slip which has no details but asking her to appear in person for an interview at the consulate. For my father, the DS160 tracking status says “Administrative Processing”.

Now what are the chances of them getting their visas? Will my dad also get his passport returned and should appear for an interview or will they process it and ask for more documents if required? What documents should my mom carry with her for her interview and what should she expect in the interview?

Has anyone been in a similar situation? What was the outcome. Please let me know. Thanks!