Why do you want to shrink volume? In fact, changing partition size is a useful practice if you want to make best of disk space on your computer. There can be multiple volumes on the disk and each works like distinct area, thus you can separate operating systems from personal data and manage data orderly. As we all know, a disk should be partitioned before we can use the space on the disk to store data.
When you have a large partition that has much free space to spare, it may make sense to spare free space from the volume by shrinking it, for instance you can either create a new partition on unallocated space or add it to other partitions. Shrinking volume refers to the task of decreasing the size of a partition, which helps to organize disk space in accordance with specific needs.
What is shrinking volume in Windows 10?.