Ntpq -p status change

Hi, my name is Nori, from Japan. I’m creating an ntp server on RasPi 4B. My RasPi is connected to GNSS sensor,
Spatial Dual by ADVANCED NAVIGATION. So my ntp server corrects its time by receiving GPS and PPS signal.

When I check the server behavior by sending ntpq -p command, it shows following status.

remote           refid      st t when poll reach   delay   offset  jitter
==================================================================
*SHM(0)          .GPS.           14 l    1   16  377    0.000    7.196   1.457
oPPS(0)          .PPS.            0 l   19   64  377    0.000   -2.369  10.883
+ntp-a3.nict.go. .NICT.           1 u   15   64  177   13.840   41.227  21.948

After a while it shows like this.

remote           refid      st t when poll reach   delay   offset  jitter
==================================================================
xSHM(0)          .GPS.           14 l    8   16  377    0.000    9.534   0.708
xPPS(0)          .PPS.            0 l   26   64  377    0.000    0.085   5.913
xntp-a3.nict.go. .NICT.           1 u   11   64  377   13.936   58.650  12.450

My question is :

(1)How does the status, “" and “o” and “+” and “x” and space, changes?
Or what condition or signal changes does ntp server use to change the status.
(2)Is the status change affected by WiFi connection?
Once WiFi is established GPS shows "”, PPS shows “o”. And if disconnected
GPS shows “*”, PPS shows “o”. Why?
(3)Even if WiFi is established, GPS and PPS shows “x” after 5 or 10 minutes. Why?
(4)I send ntpq -p command without transfering root right. Does the root right affect
the behavior (3)?

If possible please advise me any good documents I have to read.
Sorry it might be very basic knowledge, but I’m new on ntp server.

Thank you,