From Xojo Documentation
| This property is only available on platform.
For cross-platform compatibility, use ＃If...＃Endif with the Target... specifiers to make sure you will not attempt to use this property on an incompatible platform.
The value in the Copies field of the Print dialog box.
This property is only meaningful when the graphics object was created by the OpenPrinterDialog function.
On macOS this always return 1 as macOS takes care of respecting the number of copies the user requested and the app only needs to provide a single copy.