Windows 7 automatic update causes hard disk space to become smaller

Including Microsoft Windows 7 system, after using Windows for a period of time, the space of the partition where the system is located will become smaller and smaller, even if some common software is not installed to Windows 7. The partition space and hard disk space will be reduced. Although the amount of each reduction is not very large, the space occupied by the invasion is not a lot (several megabytes, more than a few GB), but why is the hard disk space slowly decreasing?

If you are familiar with the Windows 7 automatic update, you should know the reason for the screenshot below. By the way, the volume of the Windows 7 auto-update folder is constantly increasing, resulting in a smaller and smaller space for the partition where the system is located.