Windows 10 automatically manages the pagefile for your computer's configuration and the amount of RAM present in it—I'd suggest allowing the Windows OS to dynamically manage this if possible.
The minimum and maximum size of the Pagefile can be up to 1.5 times
and 4 times of the physical memory that your computer has
respectively. For example, if your computer has 1 GB of RAM, the
minimum Pagefile size can be 1.5 GB, and the maximum size of the file
can be 4 GB.
To calculate the "general rule" recommended size of virtual memory in Windows 10 per the 8 GB your system has, here's the equation 1024 x 8 x 1.5 = 12288 MB. So it sounds as if the 12 GB configured in your system currently is correct so when or if Windows needs to utilize the virtual memory, the 12 GB should suffice.
As a general rule, the maximum size of the paging file must be x1.5
the amount of RAM installed. Thus for a PC running with 4GB of RAM,
the maximum size of the swap file will be 1024 x 4 x 1.5 Mb.