Service Center (WAC 11 012 50960)
Every receipt number begins with three letters that represent the service center that received the case. There are several codes for USCIS service centers. They include:

CSC – California Service Center
EAC – Eastern Adjudication Center (now known as Vermont Service Center)
IOE – ELIS (efile)
LIN – Lincoln Service Center (now known as Nebraska Service Center)
MSC – Missouri Service Center (now known as National Benefits Center)
NBC – National Benefits Center
NSC – Nebraska Service Center
SRC – Southern Regional Center (now known as Texas Service Center)
TSC – Texas Service Center
VSC – Vermont Service Center
WAC – Western Adjudication Center (now known as California Service Center)

Fiscal Year (WAC 11 012 50960)
The second set of digits represent the fiscal year that the case was received. Government agencies use a fiscal year that is different from the calendar year. It begins on October 1 and ends on September 30. So our example case number was opened between October 2010 and September 2011.

Computer Workday (WAC 11 012 50960)
The third set of digits indicates the computer workday that the case was opened. The computer workday is basically the same thing as a workday. Therefore it excludes most weekends and holidays. Our example case was opened on the 12th workday of the 2011 fiscal year (October 18, 2010).

Case Number (WAC 11 012 50960)
The final set of five digits is the case number.

검색하다가 RECEIPT NUMBER 를 이렇게 확인한다는 글을 봤는데요
다른건 다 맞는데, 제 3번째부터 5번째 숫자( 저예시에서는 012)가 915인데 무슨뜻인가요?
COMPUTER WORKDAY가 9백번대가 나올 수가 있나요?

The receipt number of my kid also was given 900’s on computer workday.
They might assign a different number to minor dependents.