Use the SEQ command to indicate the sequence number of this file at the site of origin. The SEQ statement must come after a FILE command and should preceed any DATA commands. The "sequence number" at the origin host may simply be a spool file number, or it may have other meaning. Other meanings are implementation dependent.

The syntax is
  SEQ     sequence number  

sequence number   is typically a whole number

The sequence number will almost certainly have local dependencies and/or restrictions.
This attribute implies that the original file resided in a spooling system or was part of a group of files.