procnto at prio 63?

Hi,
I came across this pidin output:

pid tid Arguments prio STATE Blocked
1 1 /daily/x86/boot/sys/procnto 0f READY
1 2 /daily/x86/boot/sys/procnto 10r RECEIVE 1
1 3 /daily/x86/boot/sys/procnto 10r RECEIVE 1
1 4 /daily/x86/boot/sys/procnto 10r RECEIVE 1
1 5 /daily/x86/boot/sys/procnto 63r RECEIVE 1
1 6 /daily/x86/boot/sys/procnto 10r RECEIVE 1
1 7 /daily/x86/boot/sys/procnto 10r RECEIVE 1
1 8 /daily/x86/boot/sys/procnto 10r RECEIVE 1
1 9 /daily/x86/boot/sys/procnto 10r RUNNING
1 10 /daily/x86/boot/sys/procnto 6r NANOSLEEP
1 11 /daily/x86/boot/sys/procnto 10r RECEIVE 1
1 12 /daily/x86/boot/sys/procnto 11r RECEIVE 1
1 13 /daily/x86/boot/sys/procnto 10r RECEIVE 1

How can thread 5 be at prio 63? I know that procnto inherits priority, but
from whom in this case, there is no process at 63 running?
I’m asking in general because I’m using a real-time process (on a different
machine, not related to this pidin output) at prio 63 in order that nothing
(except ISRs) can interrupt it.
Am I seeing something wrong here?
Thanks
Markus