I assume by "everytime around", you mean when the zone shuts down and restarts. If not, you can still use the information below to check the exact percentage chance for the named to spawn on every respawn.
If you're not saving the zone's state when the zone dies (whether a dynamic being unloaded or the server being restarted), then when the zone restarts, it will fully repop based on the spawn tables. If we use Lord Nagafen as an example (assuming dynamic zones). If I don't save soldungb's state, I can go into the zone, kill Naggy, leave the zone, wait for the zone to shutdown, re-enter the zone, and kill him again. This is because his spawn chance is 100% and there's no saved zone state showing him as dead.
You can find spawn chances for specific mobs by running these SQL queries (and if there's an easier way or I'm wrong, please someone correct me):
Code:
SELECT * FROM npc_types WHERE name='Lord Nagafen'
which returns something like:
Code:
id name lastname level <snip>
32040 Lord_Nagafen 55 <snip>
Now, you can take the mob's id and find its spawn entry like this:
Code:
SELECT * FROM spawnentry where npcID=32040
which returns something like:
Code:
spawngroupID npcID chance
6712 32040 100
As far as I'm aware, "chance" is the mob's spawn chance percentage within that spawn group. If you query the spawngroupID, you could have multiple mobs with a chance to spawn (for example, a named/PH shared spawn point). You can query the entire spawn group like this:
Code:
SELECT * FROM spawnentry WHERE spawngroupID=6712
That will show you every npcID in that spawn group, which can be cross-referenced back to the npc_types table.
TL;DR - You need to save your zone state upon shutdown, or the server won't remember what mobs were killed when the zone is restarted. This can be done by changing the entry 'PersistentZoneState' in the 'variables' table to "1".