piped process kernel priority ( non nice prio ) - 7.3

Dear readers,

running something like `syslogc -f debug | grep there`
with syslogd configured to get some in memory logs
```
# grep debug /etc/syslog.conf
*.* :32:debug
```
The system configures the piped program at -6 Prio.

# ps ax -o pid -o pri -o command | grep '\-6'
98090 -6 cron: running job (cron)
42270 -6 cron: running job (cron)
12062 -6 /usr/local/libexec/sshg-blocker -a 30 -
34049 -6 /bin/sh /usr/local/libexec/sshg-fw-pf
67092 -6 /usr/local/libexec/sshg-parser
98864 -6 grep there

How bash | program can end up with -6 here ?
Is there a reason for that ?

Best.