This is
 ~/public_html/src/bsd/fixes/FreeBSD/src/gen/sys/netpfil/ipfw/\
  ip_fw2.c.REL=CURRENT.diff
See Also
 http://www.berklix.com/~jhs/src/bsd/fixes/FreeBSD/src/gen/sys/netinet/ipfw/
 http://www.berklix.com/~jhs/src/bsd/fixes/FreeBSD/src/gen/sys/netpfil/ipfw/\
  ip_fw2.c.REL=9.2-RELEASE.diff
  ip_fw2.c.REL=9.3-RELEASE.diff@ -> ip_fw2.c.REL=9.2-RELEASE.diff
  ip_fw2.c.REL=10.4-RELEASE.diff@ -> ip_fw2.c.REL=9.3-RELEASE.diff
  ip_fw2.c.REL=11.2-RELEASE.diff@ -> ip_fw2.c.REL=10.4-RELEASE.diff
  ip_fw2.c.REL=12.1-RELEASE.diff
  ip_fw2.c.REL=12.2-RELEASE.diff@ -> ip_fw2.c.REL=12.1-RELEASE.diff
  ip_fw2.c.REL=12.2-STABLE.diff@ -> ip_fw2.c.REL=12.1-RELEASE.diff
  ip_fw2.c.REL=12.3-RELEASE.diff@ -> ip_fw2.c.REL=12.2-RELEASE.diff
  ip_fw2.c.REL=13.0-RELEASE.diff@ -> ip_fw2.c.REL=12.2-RELEASE.diff
  ip_fw2.c.REL=CURRENT.diff

*** 13.0-CURRENT/src/sys/netpfil/ipfw/ip_fw2.c	Fri Jan 17 01:14:11 2020
--- new-generic/src/sys/netpfil/ipfw/ip_fw2.c	Wed Jan 22 03:08:46 2020
***************
*** 3362,3368 ****
  	first = IS_DEFAULT_VNET(curvnet) ? 1 : 0;
  
  	/* First set up some values that are compile time options */
! 	V_autoinc_step = 100;	/* bounded to 1..1000 in add_rule() */
  	V_fw_deny_unknown_exthdrs = 1;
  #ifdef IPFIREWALL_VERBOSE
  	V_fw_verbose = 1;
--- 3362,3369 ----
  	first = IS_DEFAULT_VNET(curvnet) ? 1 : 0;
  
  	/* First set up some values that are compile time options */
! 	// V_autoinc_step = 100;	/* bounded to 1..1000 in add_rule() */
! 	V_autoinc_step = 20;	/* bounded to 1..1000 in add_rule() */
  	V_fw_deny_unknown_exthdrs = 1;
  #ifdef IPFIREWALL_VERBOSE
  	V_fw_verbose = 1;