Each row of Policies
table declares via PolicyFlag
column if that policy is defined for system roles.
A policy can be related only with created user defined objects, UserType = 1
in User
table. System defined objects like NT AUTHORITY\SYSTEM
and Local Server Administrator aren't mapped with policies.
If you run this query:
SELECT b.username,
c.policyflag,
d.rolename,
b.usertype,
c.policyid
FROM policyuserrole a
INNER JOIN users b
ON a.userid = b.userid
INNER JOIN policies c
ON a.policyid = c.policyid
INNER JOIN roles d
ON a.roleid = d.roleid

By default you will have two rows in Policies table.
REFERENCE
Let me know if this helps.