Cisco FTD Syslog Settings

[jamie6910]

Hey guys I have some enquires on Cisco FTD.

1. What is the difference between facility level local4(20) and local0(16). What log they usually collect?
2. What will happen if we set the log level from local4(20) to local0(16), are we still able to get log messages from Local1-4?
3. Is Facility Level settings a global setting? Is it possible to set different Facility for specific syslog that we configured in FMC. 

I have been referring on the links as below. But still not sure about the definitions based on my questions. 

Reference #1  

Reference #2 

Or is it I got lost in reference? 

Thank you guys in advance.