Why does the virtual machine use 70% of the memory as soon as it starts?

Hello everyone,
I have a question，my computer system is MacOS Big Sur 11.4, parallels is 16.5.1, and memory is 16g. I only start parallels, and then the memory in parallels virtual machine immediately reaches 70%? Why? Is there anyone like me? I looked at the memory analysis, in which windows occupies 12g, but nothing is opened in windows. I suspect that the memory mechanism of parallels is based on the memory mechanism of the host computer, but the host computer is MacOS and has switched memory. Would it be a problem to use it directly? Is there a technician who can answer this question?