What exactly means the VSN PTR= "a value",  on the result of TMSBINQ running with HEADERS as control statement ?

On the report we can see:

TMC CTL REC #2      DSNBS ALLOCATED=00011130  DSNBS USED=00000007 DSNB BASE=00001257  

1ST AVAIL DSNB=00000050 VSN PTR=00001256 

Release: ONE...00200-12.6-One-TAPE MANAGEMENT
Component:

With an extended TMC we have new volume definition records between the VOLUME and DSNB records. These records can be identified by X'FF20' at offset +0 and needs to be skipped during sequential read. 

1STVDEF - RELATIVE ADDRESS IST VOLUME DEFINITION RECORD 
NUMVDEF - NUMBER OF VOLUME DEFINITION RECORDS 

The VSN PTR  points to the volume range after the last volume record and before the true first dsnb record and its the VDEF record.

If TMC Control Record #2 has a pointer to the new volume defintion records, it means that the TMC file is in a extended format. 

The following methods can be used to check for that pointer: 

* run TMSBINQ with HEADERS control statement. The pointer shows up 
in the report as 'VSN PTR=nnnnnnnn' 
 * Inquire the TMC control records in the ISPF interface. The pointer 
shows up in panel TMPITCTL as '1ST VOLDEF => nnnnnnnn' 

The VSN PTR = 0000000 means that the TMC file didn't be extended.