Depending on what you pick for your paper size choice in the Specification Options, this will determine what other options are available and used here, and which are read from the Windows printer driver.

If you pick 'Default' from the page size, that means that settings are read from the Printer driver, causing other choices you select in the Specification Options to be ignored. If you choose a specific page size (ie Letter 8.5x11) then you may find that the left margin setting has influence.

If you find that the Print Preview does not match what is actually printed on paper, this usually is related to printer driver settings.