The command is for SLU P mode only.
FEPI EXTRACT STSN gets sequence number status information for a conversation.
FEPI EXTRACT STSN >>-FEPI EXTRACT STSN--CONVID(data-value)------------------------> >--+---------------------+--+----------------------+------------> '-SEQNUMIN(data-area)-' '-SEQNUMOUT(data-area)-' >--+------------------+---------------------------------------->< '-STSNSTATUS(cvda)-'
The INVREQ condition can have the following RESP2 values: