When do you use Extended Grays in the Spyder Print software?
First, print one of the color targets (either 225 or 729 patches; I'd suggest starting with 225, to keep things simple, then try again with 729 later if you like).
If you have a printer that come with additional grey inks, we stronly recommend to use the targets with the additional Grays, as this will improve the print quality especially when these printers used their additional gryay inks and when printing b&w prints.