System Volume information is where your System Restore points and other stuff are stored.
The System Volume Information can get bloated pretty fast over time; mainly by installing and uninstalling programs.
Open the Disk Cleanup utility, go to the More Options tab and and Cleanup the System Restore.
it will delete all your restore points except the last one.
You can set the max allocated space in System Volume Information for each disk by System Restore.
Open the Control Panel and click System, or right-click on Computer / Properties. The System window will open, where you can see your WEI, comp name, etc. On the left click on System protection to open that dialog. One by one select each drive under Protection Settings and click Configure. There you can select the max amount it will use for the drive's System Volume Information folder, or none at all. I only enable it for my system drive.