The class creates a number of internal cursors (with a xl_ prefix) that contains the spreadsheet formatting and data in the default datasession. These cursors are destroyed when the class is destroyed. When a XLSX file is opened, a temporary directory is created in the local user's TEMP directory and then loaded into the cursors; after which, the temporary files and directories are removed. The same occurs when you save a XLSX file - temporary files and directories are created in TEMP directory, the ZIP file is created and renamed to XLSX extension, and then the temporary files and directories are removed.

BTW -- I am working on an update that will correct some bugs, particularly when opening a large spreadsheet. Additionally, the class currently does not read in the full current spreadsheet (it does not load images or other inserted objects). But I am working on a solution to retain all inserted objects for the next release.