In the System Configuration Boot options, the "Number of Processors" setting allows you to specify how many processors your system should use during startup. Setting this to the highest number (in your case, 12) means that the operating system will utilize all available processors when booting up, which can potentially improve performance during the startup process and for applications that can leverage multiple processors.
However, it's important to note that this setting does not directly affect the performance of your PC in everyday use unless your applications are specifically designed to take advantage of multiple processors. Most modern applications and the Windows operating system itself are capable of utilizing multiple processors effectively, so setting this option to the highest number may not harm your system and could optimize performance in scenarios where multiple processors are beneficial.
If your system has the hardware capability to support 12 processors, then setting this option should work without issues. Just ensure that your motherboard and CPU are configured correctly to handle that many processors.