GPS NTP issue

gistfile1.txt

$ ntpq -p
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
*SHM(0)          .GPS.            0 l   16   16  377    0.000   -1.389   2.475
$ ntpq -cv
ntpq 4.2.8p10@1.3728-o Sat Mar 10 18:04:53 UTC 2018 (1)
$ ntpq -c rl
associd=0 status=0418 leap_none, sync_uhf_radio, 1 event, no_sys_peer,
version="ntpd 4.2.8p10@1.3728-o Sat Mar 10 18:03:33 UTC 2018 (1)",
processor="armv7l", system="Linux/4.14.98-v7+", leap=00, stratum=1,
precision=-19, rootdelay=0.000, rootdisp=1.835, refid=GPS,
reftime=e0a0282a.8e11c62b  Mon, Jun  3 2019 16:13:46.554,
clock=e0a02837.17d520c1  Mon, Jun  3 2019 16:13:59.093, peer=49799, tc=4,
mintc=3, offset=1.205704, frequency=-2.139, sys_jitter=0.000000,
clk_jitter=1.206, clk_wander=0.475

ntp.conf

# /etc/ntp.conf, configuration for ntpd; see ntp.conf(5) for help

driftfile /var/lib/ntp/ntp.drift

# Enable this if you want statistics to be logged.
#statsdir /var/log/ntpstats/

statistics loopstats peerstats clockstats
filegen loopstats file loopstats type day enable
filegen peerstats file peerstats type day enable
filegen clockstats file clockstats type day enable


# You do need to talk to an NTP server or two (or three).
#server ntp.your-provider.example

# pool.ntp.org maps to about 1000 low-stratum NTP servers.  Your server will
# pick a different set every time it starts up.  Please consider joining the
# pool: <http://www.pool.ntp.org/join.html>
# COMMENTED OUT FOR TESTING
#pool 0.debian.pool.ntp.org iburst
#pool 1.debian.pool.ntp.org iburst
#pool 2.debian.pool.ntp.org iburst
#pool 3.debian.pool.ntp.org iburst


# Access control configuration; see /usr/share/doc/ntp-doc/html/accopt.html for
# details.  The web page <http://support.ntp.org/bin/view/Support/AccessRestrictions>
# might also be helpful.
#
# Note that "restrict" applies to both servers and clients, so a configuration
# that might be intended to block requests from certain clients could also end
# up blocking replies from your own upstream servers.

# By default, exchange time with everybody, but don't allow configuration.
restrict -4 default kod notrap nomodify nopeer noquery limited
restrict -6 default kod notrap nomodify nopeer noquery limited

# Local users may interrogate the ntp server more closely.
restrict 127.0.0.1
restrict ::1

# Needed for adding pool entries
restrict source notrap nomodify noquery

# Clients from this (example!) subnet have unlimited access, but only if
# cryptographically authenticated.
#restrict 192.168.123.0 mask 255.255.255.0 notrust


# If you want to provide time to your local subnet, change the next line.
# (Again, the address is an example only.)
#broadcast 192.168.123.255

# If you want to listen to time broadcasts on your local subnet, de-comment the
# next lines.  Please do this only if you trust everybody on the network!
#disable auth
#broadcastclient
# GPS Serial data reference
server 127.127.28.0 minpoll 4 maxpoll 4
fudge 127.127.28.0 time1 0.0 refid GPS

# GPS PPS reference
# PPS not available with USB stick!
#server 127.127.28.1 minpoll 4 maxpoll 4 prefer
#fudge 127.127.28.1 refid PPS