請教XIAOBAITU等專家--485 批準通知

小白兔等各位專家:我今天收到了USCIS來的一封通知,有關485的,具體內容如下:

The above application has been approved. Prior to receiving your permament resident card you may be required to report for biometrics processing (photo/fingerprint/signature). Please do not take any action at this time. If you are required to report for this processing, you will receive another notice advising you of the date, time and location to appear.

If you have not received your permanent resident card or the above mentioned notice to appear for biometics processing within 90 days, please call this office at the number listed below.

請問一下這種情況到底是什麽原因?我一定要去做BIOMETICS嗎?因為我七月剛剛去過.一般情況下這種情況下多長時間會收到綠卡?有出問題的可能性嗎?

先謝謝各位了!