[F1 check]求问大使馆回信中 additional AP是什么意思呢？

给大使馆发邮件问check进度，收到了模板回复，如下：

Thank you for writing to the U.S. Visa Service Desk.

We understand that your visa application status is under administrative processing.

We would like to inform you that your application requires additional administrative processing. It can take up to 60 days for the process of administrative clearance. Most administrative processing is resolved within 60 days of your visa interview, but the length of processing time will vary based on the circumstances of each case.

Please note that before inquiring about your visa status, you or your representative should wait at least 60 days from the date of your interview or the submission of supplemental documents, whichever is later. Please be patient.

请问在第三段第一句里“additional ad processing” 就单纯指的是一段check，还是check之后又来了一段extra的check？？谢谢大家！