Question: Do not fully understand --set-coall= outputs

[syberphunk]

Eg.

./ryzenadj --set-coall=-21
Successfully set coall to 4294967275

./ryzenadj --set-coall=0xFFFEB
Successfully set coall to 1048555

1. Why is it telling me two different values?
2. What exactly is set-coall doing and what is the correct value to set it for 'all cores' for 8 cores for a value of -21?

Edit: Ah for number 1. it's because the parameter expects an unsigned 32bit integer and it outputs the max value, but still does something and surprisingly accepts it?