i-94연장이라는게 뭔가요?

ㅁㄴㅇㄻ 146.***.123.115

A person may begin H1B Change of Employer upon USCIS receipt of the petition. Some employers and employees rely upon FedEx documentation of USCIS receipt of the petition the Form I-797, case filing receipt notice from USCIS often has the FedEx delivery date as the Receipt date.

인터넷에 어떤 변호사는 이렇게 말하고 또다른 변호사는 그렇지 않다고 하고 복잡하군요.