Hi papa G,
I checked some of your more recent (last 4 months) Saved Listings, and they are all auction format. To change the quantity, you will have to change them to fixed-price listings (the option is at the top of the lister page, or you can do it in bulk from the Saved Listings page).
You can technically have more than one item on an auction-style listing, but that would require you to use the old "lots" option (which is not that common anymore.)
If you have any other questions don't hesitate to contact our Customer Support (under the Help tab).