Restore_command

Question about restore_command in recovery.conf:
in documentation, it says: restore_command specifies the shell command that is executed to copy log files
back from archival storage. The command string may contain %f,which is replaced by the name of the desired log file, and %p, which is replaced by the absolute path to copy the log file to.

Thus:
restore_command='cp /mnt/server/archivedir/%f %p'
means copy source file /mnt/server/archivedir/* to %p, what is %p,is that default to some value or do I need specify that in the command?