This article explains how to configure Backup4all to remove from destination the files deleted in sources.
The option to remove from backup destination the files and folders deleted in sources, is available only for the Mirror backup type.
"Remove excluded or deleted files from backup" is located under Backup Properties->Type->Mirror and it's disabled by default.
You need to enable it if you want the deleted source files to be removed from destination.
Also please note the file deletion phase is executed at the end of the backup.
If you don't have at least one new or modified file in sources to be backed up, Backup4all will not run the actual backup, so no files will be deleted.
Please make sure there is at least 1 new or modified file in sources, to be backed up.