How to view the total volume of multiple files under MAC OS x system

We know that under the Mac OS X system of Apple Computer, pressing the shortcut key "command" + "I" after selecting the file (or right-clicking the mouse and selecting "Show Info") will pop up the file Information window. But if you select more than one file and want to see their overall product, the above method will reveal a pop-up of multiple windows, showing each file's information separately.

Want to see the file size of multiple files and other information, with Option+command+i this shortcut (or right-click, press and hold "option" and then select "Show Info") on the line. This will only open an information window that shows the aggregated information for this batch of files.