The program doesn't automatically delete the original.
I used the search shortcut, opened 7-zip manager, clicked help and then about. The menu that appeared 7-zip 9.20, so I guess I am not using the latest version?
The latest version is 15.14.
It has a checkbox "Delete files after compression" in the "Options" section (which appears to be missing from version 9.20, according to the screenshot in the question).
This option (when checked) will remove the files after they are added to the archive.
Disclaimer
I am not affiliated with 7-zip in any way, I am just an end user of the software.