The second digit refers to the particular case within the class. Here are examples common to both Microfocus and Fujitsu compilers (although there are more besides). I would check your compiler documentation.

Code	Meaning
00	Input/output operation successful
02	Duplicate record key found (READ ok)
04	Length of record too large (READ ok)
10	File AT END
14	"The valid digits of a read relative record number are greater than the size of the relative key item of the file." from Fujitsu manual - I'm not sure I what that means!
16	Program tries to read file already AT END note: Fujitsu compiler returns code "46" in this case
22	Program attempts to write a record with a key that already exists
23	Record not found
24	Program attempts to write record to a disk that is full
30	Input/output operation unsuccessful, no further information available
34	Program attempts to write record to a disk that is full
35	Program tries to open non-existant file for INPUT, I-O or EXTEND
37	Program tries to open line sequential file in I-O mode
41	Program tries to open file that is already open
42	Program tries to close file that is not open
43	Program tries to delete or rewrite a record that has not been read
44	Program tries to write or rewrite a record of incorrect length
46	Program tries to read a record where the previous read or START has failed or the AT END condition has occurred
47	Program tries to read a record from a file opened in the incorrect mode
48	Program tries to write a record from a file opened in the incorrect mode
49	Program tries to delete or rewrite a record from a file opened in the incorrect mode

To use these codes you need to include the FILE STATUS clause in the SELECT statement of the environment division:

     SELECT TEST-FILE ASSIGN TO 'TEST-DATA.DAT'
       ORGANIZATION IS SEQUENTIAL
       FILE STATUS IS W-STATUS.

Of course W-STATUS could any user name you like. It must however be defined in working storage as PIC XX, i.e. as alpha numeric and not numeric. So, if during a program run a certain input/output error occurs, rather than the program terminate, the program will simply produce an error status.
You might code:

* Here a possible danger of too big a record being moved into W-RECORD
     READ RECORD-IN INTO W-RECORD
       IF W-STATUS = "04" THEN
          DISPLAY "Over-sized record has been read"
          SET REC-XS-FLAG TO TRUE
       END-IF
     

Another example might be, when reading from an indexed file:

     READ IN-FILE
       IF W-STATUS = "23" THEN
          DISPLAY "Record not found"
       ELSE PERFORM MAIN-PROCESS
     

You could have easily have written:

     READ IN-FILE
       INVALID KEY
          DISPLAY "Record not found"
       NOT INVALID KEY PERFORM MAIN-PROCESS
     END-READ

So consider which is the best option and remember not to try and do both.

For Fujitsu compilers at least, although the program run is not terminated, the Fujitsu WINEXE enviroment will still produce a prompt indicating the error (with more detailed error codes). I'm not sure, but I suspect that this facility can be disabled. Check the user manual.